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lslect002

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<availability><p>The British Academic Spoken English (BASE) corpus was developed at the

Universities of Warwick and Reading, under the directorship of Hilary Nesi

(Centre for English Language Teacher Education, Warwick) and Paul Thompson

(Department of Applied Linguistics, Reading), with funding from BALEAP,

EURALEX, the British Academy and the Arts and Humanities Research Board. The

original recordings are held at the Universities of Warwick and Reading, and

at the Oxford Text Archive and may be consulted by bona fide researchers

upon written application to any of the holding bodies.

The BASE corpus is freely available to researchers who agree to the

following conditions:</p>

<p>1. The recordings and transcriptions should not be modified in any

way</p>

<p>2. The recordings and transcriptions should be used for research purposes

only; they should not be reproduced in teaching materials</p>

<p>3. The recordings and transcriptions should not be reproduced in full for

a wider audience/readership, although researchers are free to quote short

passages of text (up to 200 running words from any given speech event)</p>

<p>4. The corpus developers should be informed of all presentations or

publications arising from analysis of the corpus</p><p>

Researchers should acknowledge their use of the corpus using the following

form of words:

The recordings and transcriptions used in this study come from the British

Academic Spoken English (BASE) corpus, which was developed at the

Universities of Warwick and Reading under the directorship of Hilary Nesi

(Warwick) and Paul Thompson (Reading). Corpus development was assisted by

funding from the Universities of Warwick and Reading, BALEAP, EURALEX, the

British Academy and the Arts and Humanities Research Board. </p></availability>

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<date>14/01/2000</date><equipment><p>audio</p></equipment>

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<item n="speechevent">Lecture</item>

<item n="acaddept">Agricultural Botany</item>

<item n="acaddiv">ls</item>

<item n="partlevel">UG/PG</item>

<item n="module">Management of disease</item>

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<u who="nm0191"> try and run the course <pause dur="0.7"/> is <pause dur="0.2"/> by i'll give you at the there'll be a handout each week <pause dur="0.6"/> which will <pause dur="0.3"/> more or less summarize the information content <pause dur="0.4"/> that i'm trying to get across <pause dur="1.0"/> and most weeks there will be <pause dur="0.6"/> exercises <pause dur="0.8"/> # in the sense of <pause dur="0.2"/> data handling <pause dur="0.5"/> and <pause dur="0.6"/> # <pause dur="2.1"/> # <pause dur="0.8"/> written exercises <pause dur="0.7"/> for you # to try and consolidate <pause dur="0.3"/> the material <pause dur="0.5"/> in <pause dur="0.8"/> # <pause dur="0.3"/> this <pause dur="0.3"/> spoken <pause dur="0.2"/> session <pause dur="1.5"/> what i say in the spoken session <pause dur="0.3"/> should correspond almost exactly <pause dur="0.7"/> although <pause dur="0.5"/> we will take longer <pause dur="0.2"/> with what is written <pause dur="0.3"/> in the handout <pause dur="1.0"/> and <pause dur="0.9"/> but <pause dur="0.4"/> no sorry but <pause dur="1.0"/> nonetheless <pause dur="0.2"/> since there is only one <pause dur="0.3"/> of you <pause dur="0.4"/> whose native language <pause dur="0.2"/> is English <pause dur="1.9"/> if i am going too fast <pause dur="1.0"/> please ask me to slow down <pause dur="0.3"/> if i say something that you don't understand <pause dur="2.0"/> give yourself ten seconds to understand it <pause dur="0.7"/> and then ask me <pause dur="0.3"/> because it is much better <pause dur="0.3"/> if i can keep you with me i would <pause dur="0.4"/> some of the material <pause dur="0.7"/> the logic <pause dur="0.3"/> is quite complicated <pause dur="1.2"/> and if i lose you on the second step and i carry on to the end <pause dur="0.4"/> we've wasted a lot of time <pause dur="0.5"/> and you will feel depressed <pause dur="0.3"/> whereas <vocal desc="laughter" iterated="y" dur="1"/>

if i sort it out as we go alone so don't hesitate to interrupt me <pause dur="1.4"/> # <pause dur="0.5"/> the more we can do it <pause dur="0.2"/> as <pause dur="0.2"/> # a question and answer session <pause dur="0.3"/> the better <pause dur="1.0"/> if you read through <pause dur="0.3"/> the handouts <pause dur="0.4"/> before you come <pause dur="1.2"/> again <pause dur="0.4"/> i hope <pause dur="0.5"/> that will be <pause dur="0.5"/> helpful <pause dur="3.0"/> # <pause dur="0.3"/> i ought to say something about the general <pause dur="0.3"/> pattern <pause dur="0.3"/> of <pause dur="0.3"/> the course because it's been taken out of the <pause dur="0.2"/> handbook <pause dur="2.0"/> so <pause dur="0.7"/> # <pause dur="1.7"/> i'll do that on the <pause dur="0.8"/> board <pause dur="2.7"/> hope we can rub out kilodalton <pause dur="0.7"/><event desc="wipes board" iterated="y" dur="3"/> yes <pause dur="0.5"/> good <pause dur="1.3"/> oh and they've got pens here too <pause dur="0.3"/> right great <pause dur="0.7"/> okay <pause dur="2.1"/> # <pause dur="2.7"/> should have given you a handout for this <pause dur="0.3"/> sorry <pause dur="0.8"/> roughly speaking i'm going to talk about <pause dur="4.2"/> <kinesic desc="writes on board" iterated="y" dur="13"/> the population <pause dur="2.0"/> dynamics <pause dur="4.7"/> weeks one and two <pause dur="2.2"/> i'm going to talk about <pause dur="2.6"/><kinesic desc="writes on board" iterated="y" dur="2"/> yield <pause dur="1.8"/> # <pause dur="3.2"/><kinesic desc="writes on board" iterated="y" dur="17"/> disease <pause dur="2.7"/> and <pause dur="1.5"/> pathogen <pause dur="2.3"/> relations in week three <pause dur="4.1"/> i'm going to talk about <pause dur="0.8"/> the <pause dur="1.6"/><kinesic desc="writes on board" iterated="y" dur="9"/> genetic basis <pause dur="1.3"/> or the <pause dur="0.2"/> the use of <pause dur="0.6"/> genetic resistance <pause dur="1.1"/> in <pause dur="0.2"/> both as to both how it works <pause dur="2.0"/> how it can be used in populations how pathogens respond what happens in the wild <pause dur="0.3"/> so that's <pause dur="0.3"/> four <pause dur="0.4"/> five <pause dur="0.6"/> six <pause dur="1.3"/> i'm going to talk <pause dur="0.8"/> # <pause dur="1.7"/> about <pause dur="4.6"/> that may even be four

five six seven <pause dur="0.2"/> no i think it's four five six <pause dur="0.8"/> # <pause dur="2.0"/> sorry <pause dur="0.9"/> it's late in the term <pause dur="0.5"/> # i'm then going to move on to <pause dur="1.7"/> # <pause dur="0.3"/> chemistry <pause dur="3.9"/><kinesic desc="writes on board" iterated="y" dur="4"/> which i shall be spending a couple of sessions on <pause dur="2.0"/> oh it is <kinesic desc="writes on board" iterated="y" dur="1"/> seven as well <pause dur="1.0"/> genetic resistance <pause dur="1.3"/><kinesic desc="writes on board" iterated="y" dur="3"/> and <pause dur="1.3"/> that <pause dur="0.2"/> moves in by a curious piece of logic <pause dur="0.3"/> to talking about space <pause dur="0.9"/> chemistry <pause dur="1.6"/><kinesic desc="writes on board" iterated="y" dur="11"/> eight nine <pause dur="0.6"/> and then a sort of consolidation session <pause dur="4.9"/> in week ten <pause dur="1.8"/> the assessment for the course <pause dur="1.1"/> is <pause dur="0.5"/> # usually an exam <pause dur="0.3"/> # <pause dur="0.4"/> which <pause dur="0.8"/> i think you two will take <pause dur="0.8"/> are the rest of you here in the Summer term </u><pause dur="0.8"/><u who="sm0192" trans="pause"> no </u><u who="sm0193" trans="latching"> <gap reason="inaudible" extent="1 sec"/></u><pause dur="0.9"/> <u who="nm0191" trans="pause"> # <pause dur="0.9"/> okay well if you're here in the Summer term <pause dur="0.6"/> # <pause dur="1.0"/> there will be an exam <pause dur="1.5"/> and <pause dur="0.2"/> an in course assessment <pause dur="0.4"/> which takes place <pause dur="0.4"/> over these <pause dur="0.3"/> three weeks <pause dur="0.4"/> in which i ask you to manage an imaginary crop <pause dur="0.6"/> i'll explain more about how that works but <pause dur="1.1"/> basically you have to <pause dur="0.3"/> research what you would actually do in terms of <pause dur="0.4"/> planting a variety of wheat <pause dur="0.4"/> # <pause dur="1.9"/> when <pause dur="0.2"/> and what chemicals you would apply <pause dur="0.8"/> and why <pause dur="0.8"/> and i keep feeding you information about what's happening to the season and you keep telling me <pause dur="0.5"/> what's going

on as if we were running a whole year <pause dur="0.3"/> over a couple of weeks <pause dur="0.8"/> so that will happen at the end of term <pause dur="0.3"/> for those of you not taking the exam <pause dur="0.3"/> there will probably also be an essay to do <pause dur="0.5"/> over the following vacation which you can send back <pause dur="1.5"/> okay </u><pause dur="0.4"/><u who="sm0194" trans="pause"> # so this # module is going to be carried out # through the Summer term </u><pause dur="0.4"/> <u who="nm0191" trans="pause"> no </u><u who="sm0194" trans="overlap"> <gap reason="inaudible" extent="1 sec"/> </u><u who="nm0191" trans="overlap"> but <pause dur="0.2"/> the exam <pause dur="0.2"/> is timetabled <pause dur="0.2"/> in the first week of the Summer term <pause dur="1.8"/> # so if you are here in the Summer term </u><pause dur="0.5"/><u who="sm0194" trans="pause"> yes </u><u who="nm0191" trans="latching"> it will be easiest <pause dur="1.5"/> and most consistent <pause dur="0.2"/> for me <pause dur="0.6"/> if <pause dur="0.3"/> you take the exam but for those who are actually not going to be here <pause dur="0.9"/> i can't insist <shift feature="voice" new="laugh"/> you come back to do that obviously <shift feature="voice" new="normal"/> <pause dur="0.4"/> so i will set an essay type assessment <pause dur="0.2"/> instead <pause dur="2.8"/> okay <pause dur="1.3"/> am i talking clearly enough for you to understand so far </u><u who="sm0193" trans="overlap"> <vocal desc="cough" iterated="n"/> <gap reason="inaudible" extent="1 sec"/><vocal desc="cough" iterated="n"/> <pause dur="0.5"/> does not has to be hand in at week ten or </u><pause dur="0.8"/> <u who="nm0191" trans="pause"> # no i <pause dur="0.3"/> well i can arrange that if you prefer <pause dur="0.9"/> but <pause dur="0.4"/> i would <pause dur="0.6"/> i feel that the <trunc>cour</trunc> you will gain more from the course if you reflect on it a bit afterwards <pause dur="0.4"/> so i would prefer <pause dur="0.3"/> to set you an essay with a deadline three four weeks after the end of the course <pause dur="0.3"/> you <trunc>wi</trunc> <trunc>mi</trunc> may wish to complete it after

you go back to Germany <pause dur="1.0"/> and then send it by post <pause dur="1.3"/> it depends if you need to take do you need to take marks with you when you go <pause dur="1.1"/> or can we send the marks on afterwards </u><pause dur="0.6"/> <u who="sm0193" trans="pause"> i think you can send the marks afterwards </u><u who="nm0191" trans="overlap"> yes </u><u who="sm0193" trans="overlap"> because even if i hand it <pause dur="0.2"/> in at week ten <gap reason="inaudible" extent="1 sec"/></u><u who="nm0191" trans="overlap"> yeah i'm not going to mark it immediately <pause dur="0.2"/> yeah <pause dur="0.4"/> well <pause dur="1.1"/> probably not </u><u who="sm0193" trans="latching"> <gap reason="inaudible" extent="1 word"/></u><u who="nm0191" trans="overlap"> yes <vocal desc="laughter" iterated="y" dur="1"/> <pause dur="1.0"/> okay <pause dur="1.6"/> so that's the course structure <pause dur="0.3"/> # it's not a practical course <pause dur="0.5"/> # in the sense of hands on <pause dur="0.6"/> # but i hope it will engage with reality <pause dur="1.9"/> you may need to be a little bit patient <pause dur="0.3"/> about that engagement with reality <pause dur="0.3"/> because i am going to try and build up the subject systematically <pause dur="1.6"/> so <pause dur="0.6"/> i'm going to # <pause dur="0.5"/> develop things <pause dur="0.5"/> from <pause dur="1.1"/> a fairly basic <pause dur="0.4"/> point of view i'm not immediately going to say in fact i'm almost never going to say <pause dur="0.3"/> if you're growing <pause dur="0.2"/> this crop <pause dur="0.4"/> you spray this thing at such and such a time and you plant this variety <pause dur="1.0"/> i'm always going to be talking about underlying principles <pause dur="0.9"/> or almost always <pause dur="2.5"/> okay <pause dur="4.1"/> can i wipe this off <pause dur="0.4"/> now <pause dur="1.4"/> thank you <pause dur="9.7"/><event desc="wipes board" iterated="y" dur="9"/> so <pause dur="0.2"/> some of you have already picked

up that the course is entitled Management <pause dur="0.3"/> of <pause dur="0.3"/> Disease <pause dur="2.1"/> and <pause dur="1.6"/> that is a deliberate form of words <pause dur="0.7"/> i think that the best <pause dur="0.2"/> management of plant disease arises if you think of it <pause dur="0.3"/> as a management problem <pause dur="0.6"/> and not <pause dur="0.2"/> a control problem <pause dur="0.8"/> control <pause dur="0.2"/> implies <pause dur="2.3"/> right <pause dur="0.8"/> that <pause dur="0.7"/> isn't going to lead you to the most economic <pause dur="0.4"/> environmentally friendly <pause dur="0.5"/> and effective <pause dur="0.3"/> solutions <pause dur="0.5"/> the most effective solutions <pause dur="0.4"/> are ones which work <pause dur="0.2"/> with <pause dur="0.4"/> what's going on <pause dur="0.4"/> based on an understanding of what's going on <pause dur="1.1"/> and <pause dur="0.3"/> only limit disease to the extent <pause dur="0.2"/> that is necessary <pause dur="5.3"/> and in order to do this the two things that you need to know are <pause dur="1.4"/> how do you find out <pause dur="0.3"/> at any given moment <pause dur="0.2"/> in growing a crop <pause dur="0.3"/> what is the best decision <pause dur="2.7"/> and the second thing <pause dur="0.7"/> is <pause dur="1.6"/> what decisions <pause dur="0.3"/> could i possibly make <pause dur="2.8"/> okay you need to know the spectrum of things you might do <pause dur="0.5"/> and then you need to know how to choose among them <pause dur="1.8"/> and i'm going to begin with an example <pause dur="1.2"/> which will probably take me about twenty minutes or so <pause dur="0.4"/> to <pause dur="0.3"/> set out <pause dur="1.0"/> and then we'll have a short break for

you to get your brains back <pause dur="1.1"/> # and ask any questions <pause dur="0.3"/> and maybe stretch your legs and so on <pause dur="0.5"/> and then i'm going to talk you through <pause dur="0.2"/> some <pause dur="0.2"/> theory <pause dur="1.1"/> of <pause dur="1.5"/> # <pause dur="0.9"/> which will <pause dur="0.8"/> explain and provide a foundation <pause dur="0.2"/> for what i've said and for <pause dur="0.4"/> the general population dynamics <pause dur="0.6"/> of disease <pause dur="0.5"/> and that will take us to all about half past twelve <pause dur="1.8"/> okay <pause dur="1.0"/> so <pause dur="1.5"/> what i want to do as an <trunc>e</trunc> with an example <pause dur="1.3"/> is look at why it is <pause dur="0.9"/> that <pause dur="0.3"/> wheat growers <pause dur="0.6"/> in Australia <pause dur="0.9"/> do not use fungicides <pause dur="0.8"/> on their wheat <pause dur="1.1"/> but wheat growers <pause dur="0.4"/> in England <pause dur="0.8"/> or the U-K <pause dur="0.7"/> or indeed Germany <pause dur="0.5"/> apply <pause dur="0.2"/> two <pause dur="0.2"/> or three fungicides <pause dur="0.4"/> to their crops <pause dur="3.5"/> so i'll try and develop this <pause dur="0.3"/> as a contrast <pause dur="3.6"/> <kinesic desc="writes on board" iterated="y" dur="17"/> U-K <pause dur="1.9"/> Germany i'm getting obsessed <pause dur="0.5"/><event desc="student enters room" iterated="n" n="sf0195"/> Australia <pause dur="3.9"/> i say U-K <pause dur="0.3"/> that will apply to <pause dur="0.8"/> most <pause dur="0.5"/> of <pause dur="0.4"/> northern Europe <pause dur="0.4"/> <shift feature="voice" new="laugh"/> welcome </u><pause dur="0.3"/><u who="sf0195" trans="pause"> sorry <pause dur="0.2"/> so sorry <pause dur="0.8"/> </u><u who="nm0191" trans="overlap"> <shift feature="voice" new="normal"/> <trunc>abo</trunc> </u><u who="sf0195" trans="overlap"> about late # </u><pause dur="0.9"/> <u who="nm0191" trans="pause"> that's okay <pause dur="1.1"/> you are <pause dur="0.7"/> can i <pause dur="0.2"/><event desc="passes out handouts" iterated="n"/> just

pass you this so that we have a record of everyone who's here <pause dur="2.1"/> you are </u><pause dur="0.3"/> <u who="sf0195" trans="pause"> <gap reason="name" extent="1 word"/> </u><pause dur="0.6"/> <u who="nm0191" trans="pause"> <gap reason="name" extent="1 word"/> <pause dur="0.8"/> from </u><u who="sf0195" trans="overlap"> i'm a <pause dur="0.5"/> from # doing M-S-C horticulture </u><pause dur="0.3"/> <u who="nm0191" trans="pause"> M-S-C horticulture okay <pause dur="0.3"/> thank you <pause dur="3.5"/> okay <pause dur="2.5"/> the first <pause dur="0.2"/> difference and perhaps this is probably the key one <pause dur="0.8"/> is that <pause dur="0.4"/> in the U-K <pause dur="0.9"/><kinesic desc="writes on board" iterated="y" dur="13"/> we are growing <pause dur="0.2"/> our wheat <pause dur="1.0"/> with <pause dur="0.7"/> cool <pause dur="0.6"/> summer <pause dur="0.7"/> conditions <pause dur="2.3"/> the average temperature in June <pause dur="0.4"/> is fourteen degrees <pause dur="0.3"/> the average in July <pause dur="0.3"/> is eighteen <pause dur="3.3"/> whereas <pause dur="0.7"/><kinesic desc="writes on board" iterated="y" dur="7"/> in Australia <pause dur="0.4"/> you're growing <pause dur="0.2"/> under a hot <pause dur="0.6"/> summer <pause dur="1.3"/> conditions <pause dur="0.3"/> temperatures up to thirty <pause dur="0.3"/> even more <pause dur="2.5"/> because <pause dur="0.6"/> the <trunc>s</trunc> <pause dur="0.7"/> summers are hot <pause dur="0.4"/> the wheat <pause dur="0.2"/> ripens <pause dur="0.2"/> rapidly <pause dur="1.2"/> because <pause dur="0.4"/> the development <pause dur="0.2"/> of the crop <pause dur="1.8"/> depends <pause dur="0.2"/> on <pause dur="0.3"/> the temperature <pause dur="2.0"/> okay <pause dur="0.5"/> it develops very slowly at low temperatures <pause dur="0.2"/> very fast at high temperatures <pause dur="0.3"/> development in the sense of going from stage to stage <pause dur="0.2"/> in the ripening process <pause dur="4.0"/> and <pause dur="0.8"/> the days <pause dur="0.3"/><kinesic desc="writes on board" iterated="y" dur="5"/> are <pause dur="0.9"/> relatively short <pause dur="2.1"/> they're quite close to the Equator we're talking twelve or thirteen hour days <pause dur="0.7"/> whereas <pause dur="0.6"/> in the middle of the summer <pause dur="0.6"/> we're talking <pause dur="0.4"/> long <pause dur="0.5"/><kinesic desc="writes on board" iterated="y" dur="3"/> days <pause dur="1.1"/> and it's no accident <pause dur="0.4"/> that the world

record <pause dur="0.2"/> wheat yield <pause dur="0.5"/> actually comes from Scotland <pause dur="2.2"/> the further north you go <pause dur="0.3"/> with a sufficiently mild climate <pause dur="0.8"/> the better the summer yields you'll get <pause dur="0.5"/> because <pause dur="1.8"/> with a cool summer the crop develops slowly <pause dur="1.6"/> because it develops slowly <pause dur="0.4"/> and the long days <pause dur="0.2"/> there is a lot of time <pause dur="0.2"/> for <trunc>so</trunc> photosynthesis <pause dur="2.6"/> so <pause dur="0.3"/> these two together <pause dur="0.7"/> mean <pause dur="0.3"/><kinesic desc="writes on board" iterated="y" dur="6"/> a low <pause dur="0.6"/> potential <pause dur="0.6"/> yield <pause dur="2.4"/> the crop <pause dur="0.2"/> has to make <pause dur="0.4"/> all the sugars it can <pause dur="0.3"/> to <pause dur="0.2"/> fill the grain <pause dur="2.7"/> with an if if you find it <pause dur="0.3"/> i'm going to use this board <pause dur="0.3"/> it may be helpful to sit further forward if you're having <pause dur="0.4"/> having <pause dur="0.3"/> trouble seeing </u><pause dur="0.8"/> <u who="sm0196" trans="pause"> oh i can see but the <pause dur="0.6"/> <gap reason="inaudible" extent="1 sec"/></u><pause dur="0.2"/> <u who="nm0191" trans="pause"> but is the light bad <pause dur="0.2"/> shall i adjust the lighting <pause dur="0.9"/> # </u><pause dur="1.3"/> <u who="sm0197" trans="pause"> i think it's the reflects the </u><pause dur="0.5"/> <u who="sm0198" trans="pause"> yes that's it's some kind of reflection </u><pause dur="1.0"/> <u who="nm0191" trans="pause"> yes that's # hang on </u><u who="sf0199" trans="latching"> the pen is red <pause dur="0.2"/> so can't see that </u><pause dur="1.6"/>

<u who="nm0191" trans="pause"> okay the red doesn't show so i'll <pause dur="0.5"/> change that then <pause dur="0.6"/><event desc="changes lights" iterated="y" dur="12"/> # oh <pause dur="0.2"/> no i want <pause dur="0.2"/> that don't i <pause dur="0.9"/> sliders <pause dur="1.6"/> which is reflecting <pause dur="1.1"/> is that <pause dur="1.0"/> better <pause dur="0.6"/> worse </u><pause dur="0.4"/> <u who="sf0199" trans="pause"> same </u><pause dur="0.3"/> <u who="nm0191" trans="pause"> same <pause dur="1.0"/> it's just that it's red </u><u who="sm0200" trans="latching"> <gap reason="inaudible" extent="1 sec"/> </u><u who="sm0201" trans="latching"> yep <pause dur="0.2"/> change pens </u><u who="nm0191" trans="overlap"> okay change pens <pause dur="2.0"/> i like playing with the lights that's better <pause dur="0.8"/><vocal desc="laughter" n="ss" iterated="y" dur="2"/> okay change pens <pause dur="1.6"/><event desc="changes pen" iterated="n"/> aye <vocal desc="sigh" iterated="n"/> let's try <trunc>b</trunc> green <pause dur="2.9"/> <kinesic desc="writes on board" iterated="y" dur="10"/> so this just says cool <pause dur="1.4"/> summer <pause dur="3.4"/> and this says <pause dur="0.2"/> long <pause dur="0.6"/> days <pause dur="0.3"/> and they are anyway remember that this is all written down <shift feature="voice" new="laugh"/> already in the handout <pause dur="1.0"/> <shift feature="voice" new="normal"/> but <kinesic desc="writes on board" iterated="y" dur="10"/> the consequence of that is that you have <pause dur="0.3"/> a high <pause dur="0.5"/> potential <pause dur="2.9"/> yield <pause dur="5.1"/> not only that <pause dur="0.5"/> but <pause dur="0.5"/> generally speaking <pause dur="1.1"/><kinesic desc="writes on board" iterated="y" dur="8"/> water <pause dur="0.6"/> is <pause dur="0.3"/> not <pause dur="0.3"/> an important limiting factor <pause dur="3.8"/> it rains it rains all the year round <pause dur="1.4"/> whereas in Australia <pause dur="1.7"/><kinesic desc="writes on board" iterated="y" dur="27"/> with <pause dur="1.9"/> hot summers <pause dur="6.9"/> short days <pause dur="2.6"/> and therefore <pause dur="0.4"/> low <pause dur="1.1"/> potential yields <pause dur="0.8"/> there's also <pause dur="1.4"/> generally speaking <pause dur="0.3"/> a shortage of water <pause dur="0.5"/> Australia is the sort of place where wheat evolved it's quite good at surviving on relatively low amounts of

water <pause dur="0.7"/> but it doesn't encourage it <pause dur="0.4"/> to make <pause dur="0.7"/> high <pause dur="0.3"/> yields <pause dur="2.1"/><kinesic desc="writes on board" iterated="y" dur="8"/> and <pause dur="0.2"/> because <pause dur="0.6"/> the water <pause dur="0.2"/> is limited <pause dur="2.8"/> that means that fertilization <pause dur="0.4"/> and nutrient supply <pause dur="0.2"/> is not <pause dur="0.2"/> a limiting factor <pause dur="1.0"/> therefore there is no point <pause dur="0.2"/> in adding fertilizer <pause dur="1.3"/> whereas water is not limiting in the U-K <pause dur="0.6"/><kinesic desc="writes on board" iterated="y" dur="9"/> so <pause dur="0.7"/> the crop <pause dur="0.5"/> is responsive <pause dur="0.4"/> to nitrogen <pause dur="3.1"/> nitrogen <pause dur="0.2"/> generally is a limiting factor <pause dur="1.3"/> and so it <pause dur="0.2"/> pays farmers <pause dur="0.4"/> to add <pause dur="0.2"/> nitrogen <pause dur="0.7"/> and <trunc>f</trunc> frequently <pause dur="0.4"/> that would be in the region of one-hundred-and-fifty <pause dur="0.5"/><kinesic desc="writes on board" iterated="y" dur="4"/> to two-hundred-and-fifty <pause dur="0.6"/> kilos <pause dur="0.4"/> per hectare <pause dur="0.6"/> really quite a lot <pause dur="5.6"/><kinesic desc="writes on board" iterated="y" dur="9"/> unresponsive <pause dur="2.3"/> to <pause dur="0.5"/> N <pause dur="2.5"/> so <pause dur="0.3"/> this <trunc>yie</trunc> <pause dur="0.4"/> gives us <pause dur="0.6"/> average yields <pause dur="1.7"/><kinesic desc="writes on board" iterated="y" dur="1"/> i'm just abbreviating average to A-V-G-E <pause dur="0.3"/> average <pause dur="0.6"/> <kinesic desc="writes on board" iterated="y" dur="8"/> yields <pause dur="1.3"/> in the region of seven to eight tons per hectare <pause dur="1.9"/> whereas <pause dur="0.7"/> the <pause dur="1.1"/> with a good yield being <pause dur="0.5"/> ten tons <pause dur="0.9"/><kinesic desc="writes on board" iterated="y" dur="2"/> or more <pause dur="1.1"/> per hectare <pause dur="0.5"/> whereas in Australia <pause dur="0.2"/><kinesic desc="writes on board" iterated="y" dur="9"/> you're talking <pause dur="0.3"/> one to two <pause dur="0.4"/> tons <pause dur="0.5"/> per hectare <pause dur="0.4"/> with three tons <pause dur="0.4"/> being good </u><pause dur="3.8"/> <u who="sm0193" trans="pause"> i've got a question </u><pause dur="0.3"/> <u who="nm0191" trans="pause"> have it </u><pause dur="0.4"/> <u who="sm0193" trans="pause"> # <pause dur="0.6"/> the plant density in Australia </u><pause dur="0.5"/><u who="nm0191" trans="pause"> it's much lower </u><pause dur="0.9"/> <u who="sm0193" trans="pause"> and how much # are they sowing <pause dur="0.9"/> per hectare how much kilogram </u><pause dur="1.5"/>

<u who="nm0191" trans="pause"> # i <pause dur="0.3"/> couldn't give you an actual figure for the seed rate but if we're sowing <pause dur="1.2"/> two-hundred-and-fifty here i would guess they were sowing <pause dur="1.0"/> actually no i would guess they were sowing a more or less similar seed rate <pause dur="1.0"/> but the tillering <pause dur="0.3"/> will be much less effective <pause dur="0.6"/> here you would expect each seed to produce <pause dur="0.4"/> two to three tillers <pause dur="0.6"/> so you would aim for a final plant density <pause dur="0.5"/> of <pause dur="0.6"/> eight to nine-hundred stems per square metre <pause dur="1.0"/> whereas in Australia <pause dur="1.3"/> you'll be you may well be sowing the same number of plants or <pause dur="0.3"/> more or less the same number of plants <pause dur="0.2"/> but you might well get only one one-and-a-half stems <pause dur="0.2"/> per plant <pause dur="0.4"/> so you might have a density <pause dur="0.3"/> perhaps four-hundred stems per square metre <pause dur="0.2"/> in a good crop <pause dur="0.6"/> and it could be lower <pause dur="0.5"/> depending on when it <pause dur="0.2"/> runs out of water <pause dur="1.5"/> the essential point is that the limiting factors are different in Australia <pause dur="0.7"/> starting right from the top a whole sequence of things <pause dur="0.4"/> mean <pause dur="1.4"/> that the potential yields are much lower <pause dur="1.4"/> that's what i need for now <pause dur="1.8"/> now consider <pause dur="0.3"/> the question

a farmer faces <pause dur="0.4"/> when <pause dur="1.3"/><kinesic desc="writes on board" iterated="y" dur="12"/> asking <pause dur="0.7"/> shall i apply a fungicide <pause dur="0.3"/> which may cost me thirty pounds <pause dur="0.6"/> per hectare <pause dur="6.8"/> # <pause dur="1.4"/> i'm afraid i haven't revised the wheat cost <pause dur="0.5"/> on your handout <pause dur="1.3"/> but <pause dur="1.3"/> it doesn't actually alter <pause dur="0.6"/> the answers <pause dur="1.8"/> i've said that the wheat was costing a hundred pounds a ton <pause dur="0.7"/> i think the current figure is probably <pause dur="0.6"/> nearer <pause dur="0.3"/> eighty pounds if you're lucky <pause dur="2.6"/> so <pause dur="3.8"/> with wheat at <pause dur="2.1"/><kinesic desc="writes on board" iterated="y" dur="6"/> at <pause dur="0.5"/> eighty pounds <pause dur="1.5"/> per ton <pause dur="1.1"/> that fungicide cost <pause dur="5.8"/> <kinesic desc="writes on board" iterated="y" dur="19"/> # fungicide costs <pause dur="0.8"/> about <pause dur="0.6"/> four-hundred <pause dur="0.6"/> kilos <pause dur="0.9"/> nought-point-four <pause dur="0.4"/> of a ton <pause dur="2.7"/> per hectare <pause dur="1.0"/> okay <pause dur="0.5"/> what i'm doing is translating <pause dur="0.7"/> the price of the fungicide <pause dur="0.7"/> into <pause dur="0.6"/> an equivalent <pause dur="0.3"/> weight <pause dur="0.4"/> of <pause dur="1.2"/><kinesic desc="writes on board" iterated="y" dur="5"/> wheat <pause dur="4.7"/> okay you can <pause dur="0.2"/> still see it yes yeah </u><u who="sm0202" trans="overlap"> <gap reason="inaudible" extent="1 sec"/></u><pause dur="1.3"/> <u who="nm0191" trans="pause"> okay <pause dur="1.3"/> now <pause dur="0.4"/> that <pause dur="1.0"/> is around <pause dur="2.0"/> let's say roughly <pause dur="2.4"/><kinesic desc="writes on board" iterated="y" dur="9"/> a five <pause dur="0.6"/> per cent <pause dur="2.2"/> of the crop value <pause dur="1.7"/> so <pause dur="0.3"/> if <pause dur="0.3"/> applying a fungicide <pause dur="0.3"/> will increase the yield by five per cent <pause dur="0.5"/> it's worth doing <pause dur="2.1"/> so <pause dur="0.2"/> a relatively minor <pause dur="0.6"/> disease problem <pause dur="1.9"/> which reduces yield by five per cent <pause dur="1.1"/> will still be worth spraying against <pause dur="3.5"/><kinesic desc="writes on board" iterated="y" dur="3"/> and <pause dur="0.8"/> in the days

before fungicides were added <pause dur="0.7"/> before fungicides were used <pause dur="0.5"/> we have survey data <pause dur="0.5"/> showing <pause dur="0.3"/> that an <pause dur="0.2"/> average <pause dur="0.4"/> wheat crop <pause dur="1.0"/> was losing about three to ten per cent <pause dur="1.1"/> of <pause dur="0.3"/> its <pause dur="0.2"/> yield <pause dur="0.9"/> due to disease <pause dur="0.6"/> the figure could be much higher <pause dur="0.3"/> occasionally <pause dur="0.3"/> and it could be lower <pause dur="0.4"/> but on average <pause dur="1.3"/> it was a figure <pause dur="0.2"/> larger <pause dur="0.3"/> than five per cent <pause dur="1.7"/> therefore it is profitable to apply fungicides <pause dur="1.1"/> and of course <pause dur="0.3"/> once you've applied a fungicide <pause dur="0.5"/> your yield increases slightly <pause dur="0.4"/> so it is favourable to apply more nitrogen <pause dur="0.3"/> you make good use of your high <pause dur="0.6"/> water retention soils <pause dur="1.1"/> and <pause dur="0.4"/> it goes around <pause dur="1.4"/> in Australia by contrast <pause dur="1.8"/> <kinesic desc="writes on board" iterated="y" dur="7"/> fungicide <pause dur="2.1"/> costs <pause dur="2.2"/> # <pause dur="1.0"/> if we're talking let's take this <pause dur="0.7"/> # <pause dur="1.2"/> two <trunc>t</trunc> ah well let's take i took the high figure there i'll take the high figure here <pause dur="0.5"/> # <pause dur="1.1"/> you <trunc>e</trunc> we're getting a yield of <pause dur="0.6"/> two-hundred-and-forty <pause dur="3.2"/><kinesic desc="writes on board" iterated="y" dur="14"/> pounds <pause dur="0.3"/> a hectare <pause dur="2.2"/> sorry <pause dur="1.3"/> costs fifteen <pause dur="0.3"/> to twenty <pause dur="0.5"/> per cent <pause dur="1.0"/> of <pause dur="0.5"/> the crop <pause dur="1.2"/> value <pause dur="2.1"/> okay <pause dur="0.7"/> so </u><pause dur="1.2"/> <u who="sf0203" trans="pause"> # is the <pause dur="0.3"/> price of wheat in Australia the same </u><pause dur="0.9"/> <u who="nm0191" trans="pause"> yes </u><pause dur="0.3"/> <u who="sf0203" trans="pause"> <gap reason="inaudible" extent="1 sec"/></u><u who="nm0191" trans="overlap"> this is more or less the world price </u><u who="sf0203" trans="latching"> it is </u><pause dur="0.3"/> <u who="nm0191" trans="pause">

it is now <pause dur="0.2"/> yes <pause dur="0.8"/> the calculation would have been different <pause dur="0.6"/> and even more dramatic <pause dur="0.6"/> when <pause dur="0.7"/> # at current <pause dur="0.3"/> present day prices <pause dur="0.4"/> wheat in the U-K was a hundred-and-sixty pounds a ton <pause dur="0.4"/> and wheat in <shift feature="voice" new="laugh"/> Australia <pause dur="0.4"/> <shift feature="voice" new="normal"/> was <pause dur="0.2"/> a hundred pounds a ton <pause dur="1.2"/> but the E-U price the E-U support is much reduced <pause dur="0.6"/> the price of the wheat is more or less the world price <pause dur="4.0"/> so <pause dur="1.8"/> here the fungicide <pause dur="0.5"/> on average you'd have to get about twenty per cent extra yield <pause dur="1.4"/> and on average <pause dur="0.2"/> you don't <pause dur="1.2"/> so <pause dur="0.3"/> the routine management of crops in Australia <pause dur="0.4"/> does not include <pause dur="0.3"/> the use of fungicide <pause dur="5.3"/> # <pause dur="2.1"/> whereas <pause dur="0.6"/> in the U-K <pause dur="1.9"/> it's <pause dur="0.2"/> logical from this analysis that fungicide will usually be used <pause dur="0.4"/> and indeed <pause dur="0.4"/> it is <pause dur="0.7"/> # <pause dur="0.3"/> by now something like ninety-five to ninety-eight per cent <pause dur="0.4"/> of all wheat crops in the U-K <pause dur="0.2"/> except organic ones <pause dur="0.8"/> are <pause dur="0.2"/> have a fungicide applied <pause dur="1.0"/> and about two-thirds of those cases <pause dur="1.3"/> the fungicide will be profitable <pause dur="3.3"/> # <pause dur="2.1"/> there's a little footnote here <pause dur="1.1"/> for those who are actually interested in wheat management <pause dur="0.4"/> that's the general

principle <pause dur="0.5"/> okay so this is little footnote <pause dur="0.7"/> the little footnote <pause dur="0.7"/> is <pause dur="0.5"/> that <pause dur="0.5"/> the Strobilurin <pause dur="0.2"/> group <pause dur="0.2"/> of fungicides <pause dur="4.6"/><kinesic desc="writes on board" iterated="y" dur="7"/> so i'll come back to this in lecture eight <pause dur="1.0"/> Strobil<pause dur="0.3"/>urin <pause dur="1.6"/> which <pause dur="0.2"/> are a novel group of fungicides introduced <pause dur="0.3"/> in the last three or four years <pause dur="1.2"/> # <pause dur="0.3"/> give a substantial yield increase <pause dur="1.1"/> of the order of ten per cent <pause dur="0.5"/> in the absence of any detectable disease problem <pause dur="2.3"/> and therefore <vocal desc="cough" iterated="n"/><pause dur="0.7"/> it is almost always profitable <pause dur="0.3"/> to apply one of those <pause dur="0.3"/> so <pause dur="0.5"/> the actual # <pause dur="0.9"/> profitability of fungicide treatment has increased recently <pause dur="0.8"/> as has the profitability of the manufacturers of Strobilurin fungicides the A-S-F and Zeneca <pause dur="1.3"/> so <pause dur="0.3"/> people have shares in <pause dur="1.1"/> okay </u><pause dur="0.5"/> <u who="sf0203" trans="pause"> does that mean the Australians have started using this Strobilurin </u><u who="nm0191" trans="latching"> well </u><pause dur="0.6"/> <u who="sf0203" trans="pause"> so does that one give them <gap reason="inaudible" extent="1 sec"/> </u><u who="nm0191" trans="overlap"> no <pause dur="0.6"/> it wouldn't <pause dur="0.3"/> because their crop is water-limited <pause dur="0.5"/> effectively what the Strobilurin is doing is enabling you to use nitrogen better <pause dur="0.9"/> because it's keeping the crop green for longer <pause dur="0.4"/> a crop which is green for longer in Australia may actually yield less <pause dur="1.0"/> because <pause dur="0.4"/> it'll be pumping water out into the atmosphere <pause dur="0.5"/> and it

will get shrivelled <pause dur="0.3"/> and die <pause dur="0.3"/> it won't get <pause dur="0.3"/> the <pause dur="0.3"/> won't be able to translocate any photosynthesis it does do <pause dur="0.3"/> into the grain <pause dur="1.9"/> # and again <pause dur="1.4"/> # one can come back to that <pause dur="0.3"/> there are actually cases <pause dur="1.7"/> in Mediterranean climates <pause dur="0.8"/> where a small amount of disease <pause dur="0.2"/> is <pause dur="0.3"/> causes <pause dur="0.6"/> a yield increase <pause dur="2.6"/> because <pause dur="0.6"/> it <pause dur="0.3"/> improves the overall efficiency <pause dur="0.2"/> of water use <pause dur="0.3"/> by destroying leaf tissue <pause dur="3.4"/> okay so <pause dur="0.5"/> it it gets very complicated but once you're into water-limited situations there's no point in retaining a green crop for a long time <pause dur="2.4"/>

okay <pause dur="0.2"/> so <pause dur="0.5"/> this is the first half <pause dur="1.3"/> here i'm showing you <pause dur="0.5"/> that Australians won't apply fungicides for very good reasons <pause dur="0.7"/> there's a positive feedback <pause dur="0.4"/> you've got <pause dur="0.2"/> a high-yielding crop <pause dur="0.2"/> which therefore justifies expensive management which makes it even more high-yielding <pause dur="0.2"/> which means that it's justified <pause dur="0.2"/> to put in <pause dur="0.2"/> even more inputs <pause dur="0.6"/> we've got a potentially <trunc>yo</trunc> low-yielding crop <pause dur="0.4"/> which is low-yielding so it isn't justified to do anything difficult so it stays <pause dur="0.3"/> low-yielding <pause dur="0.8"/> so there's a <pause dur="0.2"/> a a positive feedback in there <pause dur="1.8"/> but <pause dur="0.9"/> this analysis <pause dur="0.4"/> doesn't apply <pause dur="0.8"/> if we're talking about <pause dur="0.4"/> genetically based <pause dur="0.5"/> resistance to disease <pause dur="0.4"/> if we're talking about the choice <pause dur="0.4"/> the management decision <pause dur="0.7"/> to plant <pause dur="0.3"/> a variety which has good disease resistance <pause dur="0.5"/> as against a variety <pause dur="0.4"/> which has <pause dur="0.2"/> worse disease resistance <pause dur="1.0"/> but <pause dur="0.2"/> is higher yielding in the absence of disease <pause dur="2.2"/> so i'm going to wipe this off now <pause dur="15.1"/><event desc="wipes board" iterated="y" dur="17"/> okay <pause dur="2.3"/> and i'm going to make the point <pause dur="0.5"/> that <pause dur="5.3"/> the yield <pause dur="1.1"/> if you're breeding <pause dur="0.4"/> a crop <pause dur="0.8"/> it's difficult to breed for

several things at once <pause dur="2.1"/> that means that <pause dur="0.3"/> if you've got <pause dur="0.9"/> a resistant crop <pause dur="4.4"/> <kinesic desc="writes on board" iterated="y" dur="9"/> and a susceptible crop <pause dur="3.0"/> you will often find <pause dur="0.2"/> that you have the situation <pause dur="0.7"/> <kinesic desc="writes on board" iterated="y" dur="16"/> where <pause dur="0.2"/> without <pause dur="0.3"/> or <pause dur="0.2"/> let's put disease <pause dur="2.3"/> without disease <pause dur="0.6"/> in the absence of the disease <pause dur="0.6"/> the susceptible crop <pause dur="2.1"/> is the best <pause dur="1.1"/> it outyields <pause dur="0.4"/> the resistant crop <pause dur="0.6"/> whereas <pause dur="0.3"/><kinesic desc="writes on board" iterated="y" dur="4"/> the situation <pause dur="0.3"/> is reversed <pause dur="1.4"/> for <pause dur="1.1"/> the case where you do have where you have disease <pause dur="2.7"/> the cost of changing a cultivar <pause dur="0.2"/> isn't usually very expensive <pause dur="0.8"/> there's small differences in seed prices <pause dur="0.4"/> but seed prices <pause dur="1.1"/> are <pause dur="1.3"/> # <pause dur="1.0"/> a percentage <pause dur="0.2"/> of the production costs the example i've written down <pause dur="0.4"/> is <pause dur="0.3"/> that if seed costs <pause dur="2.9"/> <kinesic desc="writes on board" iterated="y" dur="35"/> if <pause dur="0.4"/> seed <pause dur="0.2"/> was as much <pause dur="0.5"/> as <pause dur="0.5"/> twenty per cent <pause dur="0.7"/> of <pause dur="0.8"/> the <pause dur="0.4"/> input <pause dur="0.5"/> or production costs <pause dur="1.4"/> if it was as much as that <pause dur="1.2"/> then <pause dur="0.3"/> a ten per cent <pause dur="1.0"/> difference <pause dur="3.2"/> in <pause dur="0.4"/> seed cost <pause dur="2.7"/> would be <pause dur="0.8"/> only <pause dur="0.4"/> two <pause dur="0.4"/> per cent <pause dur="1.9"/> of your input costs <pause dur="0.4"/> so the cost of changing variety <pause dur="1.4"/> is not normally very large <pause dur="4.1"/> and therefore <pause dur="0.3"/> the continental system which we've already seen <pause dur="0.4"/> is

not <pause dur="0.2"/> able to use fungicide sensibly <pause dur="2.0"/> will therefore <pause dur="0.4"/> use a resistant variety <pause dur="0.3"/> when it's available <pause dur="0.8"/> even if <pause dur="0.3"/> there is a small premium on the seed price <pause dur="1.5"/> whereas the farmer in the high input system <pause dur="0.5"/> who's applying fungicide anyway <pause dur="0.9"/> and who only requires a small yield response from the application of fungicide <pause dur="1.0"/> will be tempted to say <pause dur="1.0"/> the fungicide's dealing with the disease <pause dur="1.3"/> i will continue to grow <pause dur="0.3"/> my susceptible variety <pause dur="3.2"/> and <pause dur="0.2"/> the example i would give of that <pause dur="0.5"/> is <pause dur="0.2"/> the <pause dur="0.4"/> wheat variety Riband <pause dur="0.4"/> in this country <pause dur="0.4"/> which is still grown i think on seventy per cent of the Scottish acreage <pause dur="0.5"/> and a substantial fraction of the English <pause dur="0.3"/> acreage <pause dur="0.3"/> sorry <pause dur="1.1"/> acreage means the same as area <vocal desc="laugh" iterated="n"/><pause dur="0.2"/> the acre is an old unit <pause dur="0.3"/> of <pause dur="0.8"/> agricultural area <pause dur="0.5"/> so and i <pause dur="0.2"/> will slip into saying it i'm sorry <pause dur="1.2"/> so seventy per cent of the <trunc>agr</trunc> of the Scottish area is sown <pause dur="0.3"/> to Riband <pause dur="0.3"/> which is <pause dur="0.5"/> appallingly <pause dur="0.3"/> susceptible <pause dur="0.5"/> to <pause dur="0.2"/> the commonest wheat disease in this country which is septoria tritici <pause dur="1.4"/> similarly <pause dur="0.3"/> # <pause dur="3.3"/> well <pause dur="0.2"/> no i'll i'll but i can <pause dur="0.3"/>

multiply examples but i i won't <pause dur="1.2"/> i won't bother <pause dur="1.0"/> # <pause dur="0.3"/> now <pause dur="0.7"/> the only caveat <pause dur="0.3"/> i want to add to that so i want to qualify this statement somewhat <pause dur="0.9"/> by saying that obviously if there is no great <pause dur="0.3"/> disadvantage <pause dur="0.4"/> to the resistance <pause dur="1.4"/> then a farmer will adopt the resistant crop as well <pause dur="0.4"/> if you can have the resistance without <pause dur="0.7"/> much yield penalty <pause dur="0.5"/> then obviously you'll take it <pause dur="1.3"/> and <pause dur="2.0"/> the phrases resistant and susceptible <pause dur="0.2"/> are always <pause dur="0.3"/> relative <pause dur="2.1"/> all of our <pause dur="1.3"/> crop protection <pause dur="0.3"/> all of our disease management is based <pause dur="0.6"/> on <pause dur="1.7"/> # <pause dur="1.2"/> crops <pause dur="0.2"/> which have <pause dur="0.3"/> very good <pause dur="0.3"/> resistance <pause dur="0.3"/> to <pause dur="0.2"/> almost all <pause dur="0.2"/> diseases <pause dur="2.4"/> chemistry <pause dur="0.5"/> chemicals <pause dur="0.4"/> can help you a bit <pause dur="1.3"/> but <pause dur="1.8"/> the <pause dur="0.3"/> closer you get to a <pause dur="0.6"/> non-resistant <pause dur="1.2"/> to a completely susceptible <pause dur="0.2"/> variety or cultivar <pause dur="0.7"/> the less <pause dur="0.3"/> effective <pause dur="0.6"/> the chemicals <pause dur="0.8"/> and other protection measures <pause dur="0.3"/> can be <pause dur="0.5"/> and if there is one message <pause dur="0.2"/> that i want to <trunc>gev</trunc> <pause dur="0.2"/> <trunc>gi</trunc> <pause dur="0.5"/> get across in this course <pause dur="0.7"/> it is <pause dur="0.4"/> that <pause dur="1.3"/> everything <pause dur="0.3"/> helps everything else if you start from a resistant crop <pause dur="1.1"/> everything else is easy <pause dur="0.9"/> if you start <pause dur="0.2"/> with a disease-susceptible

crop <pause dur="0.6"/> everything else is difficult <pause dur="0.9"/> there is no such thing as <pause dur="0.4"/> a solution <pause dur="0.4"/> a protection measure <pause dur="1.3"/> management of disease always comes in a package <pause dur="0.6"/> and comes <pause dur="0.3"/> with <pause dur="0.4"/> feedback loops <pause dur="0.3"/> like those <pause dur="0.2"/> i've described <pause dur="0.4"/> one thing <pause dur="0.2"/> leads to another thing which leads to another thing <pause dur="0.4"/> which <pause dur="0.8"/> causes you <pause dur="0.2"/> to make <pause dur="0.3"/> particular decisions <pause dur="3.5"/> if you're interested in arable crops and <pause dur="0.3"/> wheat <pause dur="0.3"/> then <pause dur="0.9"/> that <pause dur="0.3"/> example and analysis is fine <pause dur="1.0"/> but <pause dur="0.2"/> you might like to consider <pause dur="0.6"/> in particular if you're a horticulturalist <vocal desc="laugh" iterated="n"/> you might like to try and run through <pause dur="0.5"/> a similar analysis <pause dur="0.3"/> for apples <pause dur="1.1"/> where the information is fairly easily available <pause dur="0.9"/> or <pause dur="0.2"/> some other <pause dur="0.4"/> # <pause dur="0.2"/> culinary <pause dur="0.3"/> crop <pause dur="1.0"/> and there are quite interesting differences <pause dur="0.4"/> if we're talking about a bulk <pause dur="0.3"/> arable crop <pause dur="0.4"/> or if we're talking about <pause dur="0.4"/> something that is consumed <pause dur="0.5"/> as a vegetable as a culinary crop <pause dur="0.3"/> where quality considerations <pause dur="0.2"/> become more important <pause dur="0.8"/> but i will come back to that in lecture three <pause dur="2.6"/> so <pause dur="1.0"/> i've given you an example <pause dur="1.2"/> i don't want you to learn the example i

want you to pull out <pause dur="0.5"/> the general ideas <pause dur="0.4"/> by reflecting on the example </u><pause dur="0.8"/> <u who="sf0203" trans="pause"> can i just <pause dur="0.6"/> ask a question </u><u who="nm0191" trans="overlap"> do <pause dur="0.3"/> yeah </u><u who="sf0203" trans="latching"> you haven't mentioned <gap reason="inaudible" extent="2 secs"/> it's like you mentioned Riband but that's <gap reason="inaudible" extent="1 sec"/></u><u who="nm0191" trans="overlap"> but i didn't say it was because it could be sold for biscuit <shift feature="voice" new="laugh"/> in Spain <vocal desc="laughter" iterated="y" dur="1"/> </u><u who="sf0203" trans="overlap"> well yeah and because the millers like Riband as well </u><pause dur="0.3"/> <u who="nm0191" trans="pause"> yes </u><u who="sf0203" trans="latching"> it is <pause dur="0.9"/> though there's also an <gap reason="inaudible" extent="1 sec"/> </u><u who="nm0191" trans="overlap"> well <pause dur="0.2"/> our millers don't like Riband <pause dur="0.6"/> but </u><u who="sf0203" trans="overlap"> mm <pause dur="0.3"/> but <pause dur="0.7"/> but it's grown because they </u><pause dur="0.2"/> <u who="nm0191" trans="pause"> it <pause dur="0.2"/> you can <trunc>se</trunc> you can sell it for export markets <pause dur="0.3"/> </u><u who="sf0203" trans="overlap"> <trunc>m</trunc> </u><u who="nm0191" trans="overlap"> no i haven't <pause dur="0.3"/> and that's the extra factor which comes in <pause dur="0.3"/> if you start to analyse apples you can no longer leave that out <pause dur="0.6"/> wheat is simpler to consider <pause dur="1.0"/> it's easier to see the underlying principles <pause dur="0.3"/> because <pause dur="0.4"/> it is a bulk crop <pause dur="0.7"/> and although increasingly it's <pause dur="0.8"/> that that that is breaking down but <pause dur="0.3"/> you can say you just want to buy some Canadian hard red wheat <pause dur="0.8"/> and nobody worries what the variety is actually called <pause dur="0.9"/> and it makes it easier to see what's going on <pause dur="1.1"/> yeah <pause dur="2.6"/> so what were the what are the <pause dur="2.4"/> overall <pause dur="0.8"/> # <pause dur="2.8"/> what's been going on there what is a farmer doing <pause dur="0.5"/> we've got we've had a number of things that i've supplied you with <trunc>a</trunc> <pause dur="0.3"/>

answers to <pause dur="0.6"/><kinesic desc="writes on board" iterated="y" dur="11"/> so <pause dur="1.5"/> one question is <pause dur="0.4"/> how much <pause dur="0.7"/> disease <pause dur="1.2"/> is <pause dur="0.5"/> likely <pause dur="1.8"/> okay <pause dur="0.3"/> i put that in by saying <pause dur="0.2"/> that losses were around five per cent <pause dur="0.8"/> and there's <kinesic desc="writes on board" iterated="y" dur="13"/> a subsidiary question of <pause dur="0.5"/> is <pause dur="0.5"/> there <pause dur="1.0"/> a <pause dur="0.4"/> serious risk <pause dur="2.7"/> of <pause dur="0.7"/> a <pause dur="0.2"/> lot <pause dur="0.2"/> of disease <pause dur="0.8"/> in other words is there a serious risk of losing the crop <pause dur="2.6"/> which you may want to in which case people may take measures <pause dur="0.6"/> which <pause dur="0.2"/> on average <pause dur="1.0"/> costs them money <pause dur="1.3"/> it's known as an insurance premium <pause dur="1.0"/> okay <pause dur="1.2"/> insurance companies make a profit <pause dur="1.7"/> therefore <pause dur="1.2"/> on average <pause dur="0.8"/> it must cost more <pause dur="0.5"/> to insure something <pause dur="1.3"/> than to just pay for the loss when it <trunc>c</trunc> occurs <pause dur="2.6"/> the problem is that if it's your car or your house <pause dur="2.3"/> we don't have the capital <pause dur="0.4"/> to buy a new one <pause dur="0.9"/> so we opt for the option which is more expensive on average <pause dur="0.2"/> which is to pay a small amount <pause dur="0.3"/> to an insurance company <pause dur="0.6"/> they take a slice <pause dur="0.2"/> and then they pool the slices and people whose houses burn down <pause dur="0.5"/> get a large sum of money <pause dur="1.0"/> so <pause dur="0.9"/> i talked in the wheat <pause dur="0.5"/> because <pause dur="0.4"/> it's an

example where <pause dur="0.4"/> crop destruction is relatively unlikely <pause dur="0.6"/> but this kind of serious risk could modify decisions there <pause dur="0.4"/> so we need to know about both <pause dur="2.0"/> and we need to know <pause dur="2.6"/> <kinesic desc="writes on board" iterated="y" dur="13"/> what <pause dur="0.3"/> will <pause dur="0.5"/> the disease <pause dur="2.0"/> do <pause dur="0.5"/> to <pause dur="1.4"/> yield <pause dur="3.5"/> the reason i put yield <pause dur="0.3"/> in quotation marks <pause dur="1.6"/> is because some diseases will mean that you don't get much off the land <pause dur="1.8"/> other diseases <pause dur="0.2"/> will mean that you get the same amount as you would have had <pause dur="0.5"/> but you can't sell it <pause dur="2.1"/> there are lots of examples <pause dur="0.3"/> in <pause dur="0.4"/> horticulture <pause dur="0.3"/> of diseases which are completely <pause dur="0.2"/> the plant doesn't care about in the slightest <pause dur="0.9"/> but the customer won't buy it <pause dur="0.8"/> that's equivalent to a complete yield loss <pause dur="0.9"/> so <pause dur="0.5"/> when i say yield i suppose i'm meaning something like marketable yield <pause dur="1.4"/> and then you've got <pause dur="1.5"/> <kinesic desc="writes on board" iterated="y" dur="35"/> what <pause dur="1.6"/> management <pause dur="3.4"/> actions <pause dur="3.0"/> will <pause dur="1.0"/> alter <pause dur="1.6"/> disease amounts <pause dur="4.0"/>

how much do they cost <pause dur="6.9"/> and <pause dur="1.5"/> how <pause dur="0.3"/> reliable are they <pause dur="1.4"/> now <pause dur="0.9"/> this is where <pause dur="0.9"/> this course i hope where the emphasis of this course differs most <pause dur="0.4"/> from what you may have had in introductory <pause dur="0.4"/> pathology course <pause dur="1.1"/> where <pause dur="1.0"/> people tend to say oh well <pause dur="0.3"/> you can control this disease by <pause dur="0.8"/> and then there's a sort of list of things rotation chemistry whatever <pause dur="2.1"/> some of those will be completely ineffective <pause dur="0.2"/> for certain diseases <pause dur="2.3"/> or in certain settings <pause dur="1.0"/> so the question is <pause dur="1.2"/> always <pause dur="0.5"/> what things can you do which will alter disease <pause dur="0.3"/> if <pause dur="0.3"/> you take great care to plant a clean crop <pause dur="1.9"/> but the disease <pause dur="0.4"/> comes from elsewhere <pause dur="1.2"/> then <pause dur="0.3"/> you won't alter the amount of disease <pause dur="0.3"/> there's no point in spending huge amounts of money <pause dur="0.4"/> on crop hygiene on <pause dur="0.3"/> not planting infected seed <pause dur="1.0"/> if the disease is going to come from somewhere else anyway <pause dur="2.4"/> and <pause dur="0.4"/> once you know something that will work you need to know how much it will cost <pause dur="1.2"/> and you also need to know <pause dur="0.9"/> will it always work <pause dur="0.3"/> will it sometimes fail <pause dur="3.2"/> and <pause dur="0.2"/>

the answers to those questions <pause dur="0.3"/> are <pause dur="0.7"/> put <pause dur="0.8"/> in the context of <pause dur="0.9"/> managing a a growing business <pause dur="0.4"/> a a farming business <pause dur="0.2"/> or a horticultural business <pause dur="0.7"/> which has two objectives <pause dur="0.5"/> first is to stay in business <pause dur="1.7"/> which is mainly about minimizing the risks of things going wrong <pause dur="1.4"/> and then provided you can stay in business <pause dur="1.6"/> most organizations attempt to maximize their profit <pause dur="0.8"/> consistent with <pause dur="0.9"/> certain social societal pressures <pause dur="3.1"/> so <pause dur="0.7"/> that all gets a bit big <pause dur="0.2"/> what does a disease specialist need to do a disease specialist <pause dur="0.4"/> needs to know the answers <pause dur="0.6"/> to these questions <pause dur="0.2"/> in the context <pause dur="0.4"/> of their client <pause dur="1.5"/> # <pause dur="0.6"/> it mean <pause dur="0.2"/> they need to know <pause dur="0.6"/> what management options are possible <pause dur="0.8"/> what they will do <pause dur="0.3"/> how they will interact <pause dur="0.3"/> how they will interact in the system that they're looking at <pause dur="2.4"/> and you've seen the example of wheat <pause dur="0.2"/> identical crop <pause dur="0.2"/> different places completely different decisions are appropriate <pause dur="1.9"/> and <pause dur="0.6"/> the rest of the course is really concerned with setting up a situation in which we understand <pause dur="0.4"/> the answers <pause dur="0.4"/> to these questions <pause dur="5.8"/>

i'd like to give you a short break now <pause dur="0.4"/> # <pause dur="0.5"/> i am going to start talking <pause dur="1.2"/> at <pause dur="4.3"/> twelve <pause dur="1.4"/> gives you time to go to the loo and <pause dur="1.2"/> okay i'm going to start talking at twelve <pause dur="0.3"/> and i'll run for about another half hour <pause dur="2.0"/> okay i suggest </u><gap reason="break in recording" extent="uncertain"/> <u who="nm0191" trans="pause"> okay <pause dur="0.9"/> so <pause dur="0.2"/> now <pause dur="0.2"/> i'm going to try and answer the questions which i set out earlier <pause dur="1.1"/> and the first one i'm going to tackle <pause dur="0.7"/> # <pause dur="0.5"/> which is going to take me basically <pause dur="0.6"/> # this lecture the rest of this lecture and the next one <pause dur="0.8"/> is <pause dur="0.4"/> what determines <pause dur="0.3"/> how much disease <pause dur="0.2"/> there is <pause dur="0.3"/> in a crop <pause dur="2.6"/> okay <pause dur="6.3"/> and in particular <pause dur="1.2"/> <kinesic desc="writes on board" iterated="y" dur="14"/> how <pause dur="0.9"/> does <pause dur="1.0"/> it <pause dur="0.3"/> change <pause dur="2.9"/> and <pause dur="0.4"/> increase <pause dur="3.0"/> in time <pause dur="1.8"/> what i'm not going to do yet <pause dur="0.7"/> is to talk about how we actually measure <pause dur="0.3"/> disease <pause dur="1.0"/> i'm just going to assume <pause dur="0.7"/> for now <pause dur="1.1"/> that we can measure disease <pause dur="0.2"/> that we can get a number <pause dur="0.3"/> which corresponds to some notion of <pause dur="0.3"/> how much disease <pause dur="0.2"/> there is in the crop <pause dur="2.3"/> and that that measurement of <pause dur="0.3"/> how much disease there is in the crop <pause dur="0.5"/> is in some way related to how much pathogen <pause dur="0.6"/> there is in the crop <pause dur="1.1"/> and <pause dur="0.2"/> how fast it <pause dur="0.4"/> and and its capacity <pause dur="0.3"/>

to <pause dur="0.2"/> multiply <pause dur="1.5"/> so i'm going to begin <pause dur="0.5"/> by showing you <pause dur="0.4"/> some examples <pause dur="0.3"/> of <pause dur="0.3"/> how <pause dur="0.7"/> # <pause dur="0.6"/> disease <pause dur="0.4"/> builds up <pause dur="0.3"/> in time <pause dur="0.7"/> so i'm going to show you <pause dur="0.4"/> # <pause dur="1.8"/> actually a slightly more limited number than is on the back <pause dur="0.8"/> # <pause dur="1.3"/> of <pause dur="1.0"/> disease <pause dur="0.3"/> increase curves if you turn to the extreme back of the handout <pause dur="2.1"/> okay <pause dur="1.9"/> the first one i'm going to show you # <pause dur="0.2"/> i'm sorry i had <trunc>s</trunc> we have <pause dur="1.1"/> some problems <pause dur="0.4"/> # which meant that i didn't have as long to look for the overhead <pause dur="0.2"/> which turned out not to be in the place where i thought it was <pause dur="0.3"/> this morning <pause dur="0.5"/> as i should have had <pause dur="0.2"/> so i haven't got the first overhead <pause dur="1.5"/> the basic <pause dur="0.5"/> point here <pause dur="1.1"/> i'm talking about <pause dur="1.2"/> a disease called Dutch elm disease <pause dur="0.4"/> elms are large <pause dur="0.2"/> forest trees <pause dur="0.4"/> which used to be <pause dur="0.3"/> one of the commonest trees <pause dur="0.3"/> in the U-K <pause dur="0.4"/> and across northern Europe <pause dur="0.8"/> in the <pause dur="0.3"/> nineteen-seventies <pause dur="0.5"/> an epidemic <pause dur="0.4"/> of <pause dur="0.7"/> a disease called <pause dur="0.8"/> Dutch elm disease <pause dur="5.8"/> <kinesic desc="writes on board" iterated="y" dur="6"/> caused by a fungus <pause dur="1.2"/><kinesic desc="writes on board" iterated="y" dur="11"/> ophiostoma <pause dur="3.1"/> novae-<pause dur="1.8"/>ulmi <pause dur="2.0"/> fungus disease <pause dur="2.3"/> and <pause dur="0.7"/> this increased on two different varieties <pause dur="0.3"/> of <pause dur="1.0"/> elm <pause dur="0.3"/> two different species of elm <pause dur="0.6"/>

roughly <pause dur="0.6"/> like that <pause dur="0.6"/> small-leaved elm <pause dur="1.2"/> carpinifolia <pause dur="2.6"/> and <pause dur="1.2"/> what's known as the English elm <pause dur="0.3"/> ulmus <pause dur="0.7"/> procera <pause dur="1.4"/> okay <pause dur="0.3"/> an increasing curve <pause dur="3.6"/> now i do have some overheads <pause dur="5.7"/><kinesic desc="puts on transparency" iterated="n"/> here's <pause dur="0.5"/> a curve <pause dur="0.4"/> of <pause dur="0.2"/> can you see this <pause dur="0.9"/> this thing is always a </u><u who="sm0204" trans="overlap"> closer </u><u who="nm0191" trans="overlap"> a great <pause dur="0.3"/> nuisance and <pause dur="2.2"/><event desc="adjusts overhead projector" iterated="y" dur="1"/> for the less pompous among us <pause dur="1.8"/> # <pause dur="0.3"/> this is </u><pause dur="0.8"/> <u who="sf0205" trans="pause"> can you just lift it a bit higher </u><pause dur="0.7"/> <u who="nm0191" trans="pause"> yes i can </u><u who="sm0206" trans="latching"> <gap reason="inaudible" extent="1 sec"/></u><pause dur="0.4"/> <u who="nm0191" trans="pause"> it's all right <pause dur="0.3"/> it's got something on the bottom which i'll explain i'll explain this bit later <pause dur="1.0"/> okay <pause dur="1.6"/> so <pause dur="2.0"/> it's an <pause dur="0.2"/> S-<pause dur="0.2"/>shaped curve <pause dur="1.4"/> very little disease very little disease very little disease very little disease <pause dur="0.3"/> and then a very sharp and sudden increase <pause dur="0.6"/> this is a rust disease <pause dur="0.2"/> yellow rust <pause dur="0.5"/> of <pause dur="0.4"/> barley <pause dur="1.4"/> # <pause dur="0.8"/> so i <pause dur="0.3"/> take it <pause dur="0.7"/> you're all familiar with <pause dur="0.3"/> rust diseases with <pause dur="0.2"/> what a rust <pause dur="1.1"/> is puccinia yep <pause dur="1.8"/> yep </u><pause dur="0.3"/> <u who="sf0207" trans="pause"> yep <pause dur="0.7"/> <gap reason="inaudible" extent="1 sec"/></u><u who="nm0191" trans="overlap"> yep good okay <pause dur="0.9"/> <vocal dur="laugh" n="sf0207" iterated="n"/> # so it increases like that <pause dur="3.3"/><kinesic desc="changes transparency" iterated="y" dur="8"/> then a very different one <pause dur="1.2"/> # <pause dur="2.3"/> so this is a disease of cocoa <pause dur="4.0"/> in <pause dur="0.2"/> West Africa <pause dur="2.2"/> i should have drawn your attention to the time scale on this one <pause dur="1.0"/> which is running <pause dur="0.3"/> over forty days <pause dur="1.4"/> from day one-sixty of the year <pause dur="0.2"/> so

that's mid-June <pause dur="0.9"/> to <pause dur="0.2"/> the end of July <pause dur="3.3"/> whereas this <pause dur="0.5"/> is running from nineteen-forty-four <pause dur="0.2"/> to nineteen-fifty-two <pause dur="1.5"/> so that's an eight year <pause dur="0.3"/> run of data <pause dur="1.2"/> and <pause dur="0.2"/> you'll see that there's a general <pause dur="0.5"/> S-<pause dur="0.4"/>shaped curve <pause dur="0.9"/> with most rapid increase <pause dur="0.4"/> in the mid-nineteen-forties <pause dur="3.9"/><kinesic desc="changes transparency" iterated="y" dur="7"/> here's one from even earlier <pause dur="2.0"/> this is <pause dur="0.2"/> cotton <pause dur="2.9"/> i should have said that <pause dur="3.2"/><kinesic desc="writes on board" iterated="y" dur="8"/> P-<pause dur="1.1"/>omnivorum <pause dur="1.7"/> on <pause dur="0.7"/> cotton <pause dur="3.2"/> between <pause dur="0.5"/> nineteen-thirty-seven and nineteen-forty-one <pause dur="0.3"/>

so this is <pause dur="0.2"/> repeated crops <pause dur="0.5"/> of cotton <pause dur="0.4"/> planted each year <pause dur="1.0"/> but planted <pause dur="0.8"/> in the same general area <pause dur="0.9"/> whereas <pause dur="0.2"/> the cocoa swollen shoot <pause dur="0.7"/> is a tree crop <pause dur="0.4"/> those trees were all there at the beginning and they're all there at the end <pause dur="2.7"/><kinesic desc="changes transparency" iterated="y" dur="2"/> and <pause dur="0.3"/> you see <pause dur="0.2"/> again <pause dur="0.5"/> this <pause dur="0.4"/> low level to begin with <pause dur="0.4"/> and then a period of very rapid increase <pause dur="2.4"/> and the final example <pause dur="0.8"/> is <pause dur="3.0"/><event desc="looks through transparencies" iterated="y" dur="30"/> P-I-<pause dur="0.3"/>two where's P-I-one <pause dur="4.7"/> where indeed is <shift feature="voice" new="whisp"/>P-I <pause dur="3.3"/> <shift feature="voice" new="normal"/> had it this morning <pause dur="4.5"/> sorry this is <pause dur="0.2"/> classic <pause dur="1.1"/> which i should not be doing at this stage <pause dur="8.1"/> the final example <pause dur="0.3"/> then <pause dur="0.7"/> appears on your handout <pause dur="1.1"/> over the page <pause dur="2.8"/> at the bottom <pause dur="0.5"/> and is potato blight <pause dur="0.3"/> phytophthora infestans <pause dur="0.3"/> on potato <pause dur="3.7"/> showing <pause dur="1.1"/> an increasing curve <pause dur="0.8"/> over a time scale <pause dur="0.7"/> of around <pause dur="0.9"/> fifty days <pause dur="0.7"/> reaching <pause dur="0.6"/> about <pause dur="0.4"/> fifty per cent <pause dur="0.2"/> or nought-point-five <pause dur="0.4"/> severity <pause dur="1.8"/> oh here it is <pause dur="0.6"/> sorry <pause dur="2.1"/><kinesic desc="changes transparency" iterated="y" dur="3"/> put it out ready and then took the <pause dur="0.2"/> board away <pause dur="0.4"/> there you go <pause dur="0.6"/> so <pause dur="0.4"/> that is a hundred per cent severity <pause dur="2.3"/> that is

fifty per cent severity <pause dur="0.9"/> that's none <pause dur="1.1"/> okay <pause dur="0.6"/> so we have an <pause dur="0.2"/> increasing curve going up fastest <pause dur="0.2"/> at the end <pause dur="8.2"/> now what i want to do <pause dur="0.9"/> is <pause dur="0.5"/> ask <pause dur="0.5"/> is that what we expect <pause dur="2.1"/> and not only is that what we expect <pause dur="0.5"/> but how can we describe <pause dur="0.4"/> these <pause dur="0.3"/> different <pause dur="0.5"/> curves <pause dur="3.6"/> so <pause dur="0.3"/> the <trunc>arg</trunc> the the method of of reasoning i'm going to use is one that you may not have come across too much in biology <pause dur="0.4"/> it's to start from <pause dur="0.8"/> some assumptions <pause dur="2.5"/> use those assumptions to argue <pause dur="1.2"/> for <pause dur="0.3"/> what we would expect <pause dur="0.4"/> to happen <pause dur="0.4"/> in a crop <pause dur="1.6"/> and then <pause dur="0.2"/> compare our expectation <pause dur="0.4"/> with reality <pause dur="0.9"/> in order to find out how things are different <pause dur="1.6"/> and as it happens <pause dur="0.4"/> this reasoning process will also allow us to describe <pause dur="0.4"/> all of these different situations <pause dur="1.6"/> disease which increases over ten years <pause dur="0.3"/> disease which increases over twenty days <pause dur="0.7"/> by <pause dur="0.3"/> one number <pause dur="3.6"/> okay <pause dur="1.4"/> so <pause dur="2.9"/> imagine <pause dur="0.7"/> a pathogen individual <pause dur="1.3"/> in an otherwise healthy crop <pause dur="2.2"/> so <pause dur="0.7"/> # <pause dur="0.7"/> i think i'll do this <pause dur="0.9"/> on the board <pause dur="6.9"/> so i'm

going to draw a little <pause dur="0.4"/> imaginary crop on the board <pause dur="0.8"/><kinesic desc="writes on board" iterated="y" dur="1"/> in green <pause dur="1.0"/> here are my plants <pause dur="13.8"/> <kinesic desc="writes on board" iterated="y" dur="14"/> okay <pause dur="1.0"/> and <pause dur="0.7"/> one of them <pause dur="1.3"/> becomes <pause dur="1.1"/> diseased <pause dur="2.3"/><kinesic desc="writes on board" iterated="y" dur="1"/> for some reason <pause dur="4.2"/> now <pause dur="0.2"/> this <pause dur="1.3"/> disease this pathogen <pause dur="0.2"/> must have some way of propagating itself <pause dur="2.6"/> either spores <pause dur="0.3"/> or <pause dur="0.3"/> vectors <pause dur="0.3"/> if it's a virus <pause dur="2.3"/> and let's suppose <pause dur="0.6"/> so i'm talking an imaginary situation at the moment <pause dur="0.5"/> imagine that <pause dur="0.7"/> a week later <pause dur="1.1"/> its spores <pause dur="0.5"/> have infected <pause dur="1.4"/> <kinesic desc="writes on board" iterated="y" dur="5"/> two <pause dur="0.5"/> other <pause dur="0.3"/> individuals <pause dur="2.8"/> so in the week one <pause dur="5.5"/> in week <pause dur="3.3"/><kinesic desc="writes on board" iterated="y" dur="18"/> one <pause dur="0.6"/> we had <pause dur="0.6"/> one individual <pause dur="1.4"/> in week <pause dur="0.2"/> two <pause dur="0.5"/> we've got <pause dur="0.3"/> three <pause dur="2.5"/> and i'll just put in the new ones <pause dur="0.3"/> which is two <pause dur="1.0"/> one new one in week one two new ones in week two <pause dur="0.6"/> now <pause dur="2.9"/> all <pause dur="0.2"/> of these <pause dur="0.3"/> if <pause dur="0.2"/> nothing changes <pause dur="0.2"/> okay <pause dur="0.5"/> i'm specifically trying to argue <pause dur="0.4"/> if <pause dur="0.2"/> nothing changes <pause dur="2.5"/> in week <pause dur="0.2"/> three <pause dur="2.8"/> these two <pause dur="0.9"/> will each <pause dur="0.4"/> infect <pause dur="1.0"/> two more plants <pause dur="1.3"/> on average <pause dur="4.1"/><kinesic desc="writes on board" iterated="y" dur="4"/> because if this one infected two plants over a period of week and nothing else changes <pause dur="0.9"/> there's no reason <pause dur="0.4"/> why <pause dur="0.5"/> these <pause dur="0.3"/> won't infect two more plants <pause dur="0.2"/> in another week <pause dur="1.3"/> so in

week three <pause dur="0.2"/><kinesic desc="writes on board" iterated="y" dur="1"/> we're going to have <pause dur="0.8"/> # <pause dur="2.2"/> if we assume it's probably simplest to make them die after the first week <pause dur="1.5"/> though the sums come out the same <pause dur="0.7"/> we'll have four <pause dur="0.2"/> new <pause dur="0.9"/> diseased individuals <pause dur="3.2"/><kinesic desc="writes on board" iterated="y" dur="2"/> okay <pause dur="1.0"/> so what will happen in week four <pause dur="1.4"/> each of the new diseased ones <pause dur="0.3"/> becomes infectious <pause dur="0.2"/> is producing spores <pause dur="1.6"/> so what number should i write here </u><pause dur="4.6"/> <u who="sm0208" trans="pause"> can you repeat that please </u><pause dur="0.7"/><u who="sf0209" trans="pause"> yes </u> <pause dur="0.8"/> <u who="nm0191" trans="pause"> okay <pause dur="0.7"/> in week four <pause dur="0.7"/> each of the four new infections <pause dur="0.2"/> that occurred in week three <pause dur="0.5"/> will become infectious <pause dur="0.3"/> will start producing spores </u><pause dur="0.4"/> <u who="sf0209" trans="pause"> will contaminate another two</u><pause dur="0.4"/> <u who="nm0191" trans="pause"> so they will each contaminate another two <pause dur="0.2"/> so what number goes here </u><pause dur="0.5"/> <u who="sm0194" trans="pause"> <trunc>two</trunc> twelve </u><pause dur="0.5"/><u who="sf0209" trans="pause"> eight </u> <u who="nm0191" trans="latching"> eight <kinesic desc="writes on board" iterated="y" dur="3"/></u><u who="ss" trans="latching"> <gap reason="inaudible, multiple speakers" extent="1 sec"/></u><u who="nm0191" trans="overlap"> exactly <pause dur="0.9"/> yeah </u><u who="sm0194" trans="overlap"> <gap reason="inaudible" extent="1 sec"/></u><pause dur="2.3"/> <u who="sf0209" trans="pause"> <gap reason="inaudible" extent="5 secs"/> </u><pause dur="0.3"/> <u who="nm0191" trans="pause"> population <pause dur="0.2"/> sorry </u><pause dur="0.4"/> <u who="sf0210" trans="pause"> <gap reason="inaudible" extent="1 sec"/></u><pause dur="2.6"/> <u who="sm0194" trans="pause"> <gap reason="inaudible" extent="1 word"/> the infection <pause dur="0.9"/> <gap reason="inaudible" extent="1 sec"/></u><pause dur="1.3"/> <u who="nm0191" trans="pause"> and then it says <pause dur="0.2"/> new <pause dur="1.5"/> # <pause dur="2.3"/> okay <pause dur="5.0"/> so <pause dur="0.8"/> what we have here <pause dur="1.5"/> is <pause dur="0.3"/> an exponential <pause dur="0.4"/> progression <pause dur="5.9"/> so <pause dur="1.7"/> what we'd expect <pause dur="1.1"/> is that <pause dur="1.1"/><kinesic desc="writes on board" iterated="y" dur="2"/> if <pause dur="0.4"/> nothing else <pause dur="0.2"/> changed <pause dur="1.2"/> disease <pause dur="0.2"/> would grow <pause dur="0.7"/><kinesic desc="writes on board" iterated="y" dur="2"/> exponentially <pause dur="0.8"/> it would go <pause dur="0.8"/>

on whatever time scale was appropriate <pause dur="1.1"/> it would go <pause dur="0.4"/> something like <pause dur="0.2"/> one <pause dur="8.5"/> it would go one <pause dur="1.1"/> ah that's two that's where i've gone wrong <vocal desc="laughter" iterated="y" dur="1"/><pause dur="0.4"/> knew there was something funny about this <pause dur="3.5"/><kinesic desc="writes on board" iterated="y" dur="11"/> two <pause dur="1.2"/> four <pause dur="1.1"/> eight <pause dur="3.3"/> sixteen <pause dur="0.2"/> okay an exponential <pause dur="0.2"/> increase </u><pause dur="0.5"/> <u who="sf0209" trans="pause"> <gap reason="inaudible" extent="1 sec"/> quite the imaginary though isn't it</u><u who="nm0191" trans="latching"> <trunc>i</trunc> </u><pause dur="0.3"/> <u who="sf0209" trans="pause"> even the if you don't use like # # if you don't like use fungicide i mean <pause dur="0.8"/> then </u><u who="nm0191" trans="latching"> even if you use fungicide <pause dur="0.8"/> </u><u who="sf0209" trans="overlap"> <gap reason="inaudible" extent="1 sec"/></u><u who="nm0191" trans="overlap"> the effect will be <pause dur="0.4"/> that instead of <pause dur="0.4"/> each <pause dur="0.3"/> diseased individual succeeding <pause dur="0.4"/> in infecting <pause dur="0.8"/> two more <pause dur="0.7"/> each diseased individual <pause dur="0.4"/> may only infect </u><u who="sf0209" trans="latching"> one more</u><u who="nm0191" trans="overlap"> half or one <pause dur="1.0"/> that does not <pause dur="0.2"/> alter <pause dur="0.3"/> the argument <pause dur="0.3"/> that it should be <pause dur="0.5"/> an exponential <pause dur="0.5"/> but bear with me <pause dur="0.2"/> because i have pointed out that i'm trying to argue <pause dur="0.3"/> what we would expect to happen <pause dur="0.6"/> if <pause dur="0.2"/> we didn't change anything </u><pause dur="0.5"/> <u who="sf0209" trans="pause"> <gap reason="inaudible" extent="1 sec"/></u><u who="nm0191" trans="overlap"> and it's worth <pause dur="0.2"/> arguing that through <pause dur="0.9"/> because otherwise <pause dur="1.8"/> when you look at a <pause dur="0.9"/> i maybe i should have <pause dur="1.4"/> done it like this <pause dur="2.0"/><kinesic desc="changes transparency" iterated="y" dur="3"/> if i put <pause dur="0.4"/> this up <pause dur="3.2"/> the farmer's <pause dur="0.3"/> field <pause dur="0.8"/> in

mid-June <pause dur="0.3"/> was free of disease <pause dur="1.8"/> two weeks later it was nearly free of disease <pause dur="1.2"/> three weeks later <pause dur="0.2"/> it was completely devastated <pause dur="1.0"/> the natural question to ask <pause dur="2.3"/> is <pause dur="0.4"/> what happened here <pause dur="1.6"/> and <pause dur="0.2"/> if you <pause dur="0.2"/> go out <pause dur="0.4"/> into the field and start looking for <pause dur="0.3"/> funny weather conditions <pause dur="0.9"/> in that <pause dur="0.4"/> you're going to find them <pause dur="1.0"/> if you look for an eclipse of the moon <pause dur="0.2"/> you may find it <pause dur="1.0"/> if you look for <pause dur="0.8"/> # <pause dur="2.0"/> somebody who <trunc>wal</trunc> a black cat walked in front of me <pause dur="0.4"/> you'll find it <pause dur="0.2"/> you will be able to find something strange <pause dur="0.4"/> about <pause dur="0.4"/> that period <pause dur="1.2"/> but the question is <pause dur="1.1"/> did anything funny happen there <pause dur="1.5"/> and that's why i'm trying to work out <pause dur="0.3"/> not <pause dur="1.3"/> because <pause dur="1.1"/> the argument that something funny happens there <pause dur="0.3"/> is actually based on an implicit assumption <pause dur="2.9"/> <kinesic desc="writes on board" iterated="y" dur="1"/> if somebody thinks something funny happened here <kinesic desc="writes on board" iterated="n"/><pause dur="2.2"/> they're saying <pause dur="0.3"/> well what i would have expected <pause dur="0.5"/> is <pause dur="1.2"/> that <pause dur="2.2"/> i am saying <pause dur="0.3"/> well let's just think about that <pause dur="0.3"/> what would we expect <pause dur="0.7"/> and so far <pause dur="0.6"/> i've established <pause dur="0.4"/> that we would expect <pause dur="0.3"/> exponential growth <pause dur="0.2"/> initially <pause dur="5.1"/>

yeah </u><pause dur="1.0"/> <u who="sm0194" trans="pause"> sorry # so we have to determine which factors # # has # <pause dur="0.4"/> an effect # to the rapid development of the disease <pause dur="0.4"/> that case</u><pause dur="0.8"/> <u who="nm0191" trans="pause"> well <pause dur="0.2"/> but what i'm arguing <pause dur="0.3"/> is <pause dur="0.2"/> that no let let me finish constructing <pause dur="0.2"/> the </u><u who="sm0194" trans="overlap"> <gap reason="inaudible" extent="1 word"/> </u><u who="nm0191" trans="overlap"> no no no it's all right sorry you're getting the point <pause dur="1.1"/> but <pause dur="0.5"/> the point that's what you would <pause dur="0.2"/> you would tend to say okay what factors cause the rapid increase <pause dur="0.3"/> i'm saying <pause dur="0.5"/> i don't yet know <pause dur="0.2"/> whether there is a rapid increase i don't yet know <pause dur="0.3"/> whether anything changed <pause dur="0.3"/> because i don't know <pause dur="0.4"/> what to expect <pause dur="0.4"/> from <pause dur="0.2"/> a disease <pause dur="0.5"/> what would i expect disease progression in a field where nothing changed <pause dur="0.3"/> to be like <pause dur="1.7"/> okay <pause dur="0.3"/> we are very used to the idea <pause dur="0.4"/> that <pause dur="0.6"/> if nothing happens <pause dur="0.9"/> things stay as they are <pause dur="2.2"/> but <pause dur="0.2"/> when you learned physics in school <pause dur="1.6"/> and we're also used to the idea <pause dur="1.8"/><event desc="drops pen" iterated="n"/> that if you drop something <pause dur="0.6"/> it'll fall <pause dur="0.7"/> but when you learned physics in school <pause dur="0.7"/> you did a lot of thought experiments <pause dur="0.6"/> in which <pause dur="0.5"/> the teacher said contrary to all <pause dur="0.4"/> everything you knew <pause dur="0.5"/> that if no

force acted on an object <pause dur="0.9"/> it would stay where it was <pause dur="1.7"/> yeah <pause dur="0.9"/> and they said <pause dur="0.9"/> so if you were out in space and not on Earth <pause dur="0.2"/> and you let go of the pencil <pause dur="0.6"/> it would just <pause dur="0.5"/> stay where it is <pause dur="1.6"/> it doesn't stay whether it is therefore okay so there's a whole lot of thought experiments going on in the background <pause dur="0.3"/> if you were out in space and let the pencil go <pause dur="0.4"/> what would happen to it <pause dur="0.7"/> the answer is nothing <pause dur="0.4"/> therefore <pause dur="0.7"/><event desc="drops pen" iterated="n"/> there must be something acting <pause dur="0.3"/> to make it fall <pause dur="0.5"/> i want to do the same kind of thing <pause dur="0.3"/> i want to construct <pause dur="0.3"/> a rational expectation <pause dur="0.3"/> of what would happen in a field <pause dur="1.3"/><kinesic desc="writes on board" iterated="y" dur="7"/> which we can then use <pause dur="0.3"/> to compare <pause dur="0.2"/> against what we actually see <pause dur="2.0"/>

okay <pause dur="2.0"/> and so far i've shown <pause dur="0.4"/> that <pause dur="1.2"/> i've got <pause dur="1.4"/> what i would expect <pause dur="0.4"/> is that <pause dur="0.3"/><kinesic desc="writes on board" iterated="y" dur="7"/> the log <pause dur="1.6"/> of the population <pause dur="3.5"/> will <pause dur="0.6"/> increase in a straight line <pause dur="1.1"/> initially <pause dur="1.6"/> because i have <pause dur="0.2"/> exponential growth <pause dur="3.3"/> but <pause dur="0.4"/> of course <pause dur="0.3"/> once disease <pause dur="0.3"/> is <pause dur="0.4"/> really common <pause dur="3.9"/> lots of these spores <pause dur="0.9"/> will start to fall <pause dur="0.5"/> on tissue <pause dur="0.2"/> which is already infected <pause dur="3.4"/> yeah <pause dur="0.5"/> is that <pause dur="1.1"/> and <pause dur="0.4"/> one way to see what effect <pause dur="0.4"/> we would expect that to have <pause dur="0.8"/> is to say okay imagine a field which is half infected <pause dur="0.7"/> half diseased <pause dur="1.7"/> the diseased material produces spores <pause dur="0.4"/> or vectors <pause dur="0.7"/> which fall randomly all over the field <pause dur="4.0"/><kinesic desc="writes on board" iterated="y" dur="2"/> half of those <pause dur="0.2"/> will therefore fall on infected material <pause dur="2.4"/> and won't <pause dur="0.2"/> produce any new disease <pause dur="2.8"/> so the rate of increase of the disease <pause dur="0.9"/> will <pause dur="1.1"/> decrease <pause dur="0.6"/> in proportion <pause dur="1.7"/> to the diseased <pause dur="0.4"/> fraction <pause dur="0.2"/> of the field <pause dur="2.7"/> as disease becomes <pause dur="2.4"/> if it's increasing <kinesic desc="writes on board" iterated="y" dur="10"/> exponentially <pause dur="3.3"/> as <pause dur="0.3"/> it becomes commoner <pause dur="0.9"/> the rate of that exponential will fall off <pause dur="0.5"/> until <pause dur="0.3"/> when almost the whole field is infected <pause dur="0.5"/> almost no spores will be able to cause any new disease <pause dur="0.2"/> because they can't find a host <pause dur="2.2"/> so the shape we expect is something

that starts off exponential <pause dur="0.6"/> and then <pause dur="0.3"/> turns over <pause dur="2.3"/> and <pause dur="1.1"/> a little mathematics <pause dur="1.4"/> which might be a dangerous thing but a little mathematics <pause dur="1.1"/> shows <pause dur="0.6"/> that <pause dur="5.8"/> the <pause dur="0.7"/> logarithm <pause dur="1.8"/> of the healthy fraction <pause dur="1.1"/> of the diseased fraction over the healthy fraction <pause dur="1.3"/> increases <pause dur="0.2"/> smoothly <pause dur="0.3"/> with <pause dur="0.3"/> time <pause dur="1.0"/> that's <pause dur="0.3"/> equation one on your handout <pause dur="10.3"/> so <pause dur="2.9"/> if <pause dur="2.7"/><kinesic desc="writes on board" iterated="y" dur="1:14"/> nothing changes <pause dur="5.6"/> in <pause dur="0.5"/> the <pause dur="0.6"/> host-<pause dur="1.7"/>pathogen <pause dur="3.2"/> relation <pause dur="3.7"/> and <pause dur="1.0"/> if <pause dur="0.7"/> spores <pause dur="0.9"/> or vectors <pause dur="1.6"/> are evenly <pause dur="1.8"/> distributed <pause dur="3.6"/> over the whole area <pause dur="1.0"/> we expect <pause dur="2.7"/> the logarithm <pause dur="1.7"/> of the <pause dur="0.5"/> diseased <pause dur="2.0"/> fraction <pause dur="3.3"/> over the healthy <pause dur="2.0"/> fraction <pause dur="3.9"/> to increase <pause dur="2.6"/> steadily <pause dur="3.0"/> with <pause dur="1.6"/> time <pause dur="1.4"/> okay <pause dur="0.5"/> and that's written out in mathematical symbols <pause dur="0.5"/> as <pause dur="0.2"/> equation one <pause dur="2.9"/> and this thing here <pause dur="3.7"/> has a name <pause dur="0.3"/> because we use it quite commonly <pause dur="1.9"/> <kinesic desc="writes on board" iterated="y" dur="17"/> it's called <pause dur="0.6"/> the logit <pause dur="1.4"/> not the log <pause dur="0.4"/> but the logit <pause dur="0.8"/> of <pause dur="0.7"/> the <pause dur="0.7"/> diseased <pause dur="2.1"/> fraction <pause dur="3.8"/> okay <pause dur="1.9"/> now <pause dur="1.3"/> what i've done there <pause dur="0.3"/> is just <pause dur="0.3"/> argue <pause dur="5.6"/> informally <pause dur="0.3"/> and then <pause dur="0.6"/> if you wish <pause dur="0.2"/> you can see what the formal mathematical argument is <pause dur="1.6"/> what <pause dur="0.6"/> should happen <pause dur="0.7"/> if <pause dur="0.2"/> certain conditions hold <pause dur="4.7"/> now <pause dur="2.7"/><kinesic desc="changes transparency" iterated="y" dur="2"/>

here <pause dur="1.1"/> is the yellow rust case <pause dur="2.8"/> here's the original data <pause dur="1.9"/> and here it is <pause dur="0.4"/> replotted <pause dur="1.0"/> on <pause dur="0.5"/> a new scale in which <pause dur="0.2"/> this is <pause dur="0.3"/> logit <pause dur="0.4"/> of <pause dur="0.5"/> disease <pause dur="11.7"/><kinesic desc="writes on board" iterated="y" dur="6"/> okay <pause dur="1.3"/> it doesn't matter what the actual numbers work out at to # work out at <pause dur="0.7"/> the important point is <pause dur="0.8"/> that it's a straight line </u><pause dur="1.7"/><u who="sm0193" trans="pause"> and where <pause dur="0.2"/> course there is # <pause dur="0.4"/> half of the field <pause dur="0.4"/> filled with disease </u><pause dur="0.3"/><u who="nm0191" trans="pause"> no no no no <pause dur="0.3"/> sorry <shift feature="voice" new="laugh"/> that was a <pause dur="0.3"/><shift feature="voice" new="normal"/> that was the <pause dur="0.2"/> easiest case to see <pause dur="1.1"/> here <pause dur="0.2"/> there is a very small proportion of the field filled with the disease <pause dur="1.0"/> here ninety per cent of it is filled with the disease and <pause dur="0.4"/> just there <vocal desc="laugh" iterated="n"/><pause dur="0.2"/> only on that one occasion is half filled with disease </u><pause dur="0.8"/><u who="sm0193" trans="pause"> yeah i thought about # <pause dur="0.2"/> the log <pause dur="0.2"/> of <pause dur="0.2"/> disease fraction of </u><pause dur="0.4"/><u who="nm0191" trans="pause"> divided by the healthy </u><pause dur="0.2"/> <u who="sm0193" trans="pause"> yes <pause dur="0.4"/> then it's one to one and</u><u who="nm0191" trans="latching"> no <pause dur="0.6"/> if the diseased fraction is <pause dur="0.4"/> let's do some examples <pause dur="2.3"/> if the diseased fraction <pause dur="1.1"/> is nought-point-one <pause dur="2.6"/> <kinesic desc="writes on board" iterated="y" dur="11"/> then this thing <pause dur="0.6"/> is <pause dur="0.3"/> log <pause dur="0.8"/> of nought-point-one <pause dur="0.6"/> divided by <pause dur="0.2"/> nought-point-nine </u><pause dur="1.3"/><u who="sm0193" trans="pause"> no i thought about <pause dur="0.2"/> # <pause dur="0.4"/> if half of <pause dur="0.2"/> the field is</u> <u who="nm0191" trans="latching"> yes </u><pause dur="0.6"/> <u who="sm0193" trans="pause"> diseased</u><u who="nm0191" trans="latching"> yes </u><pause dur="0.2"/> <u who="sm0193" trans="pause"> then we have <pause dur="0.3"/> O-point-five</u><pause dur="0.8"/> <u who="nm0191" trans="pause"> yes </u><u who="sm0193" trans="overlap"> diseased fraction</u><pause dur="0.3"/> <u who="nm0191" trans="pause"> yes </u><u who="sm0193" trans="latching"> and <trunc>O-point-f</trunc> O-point-five healthy fraction </u><u who="nm0191" trans="overlap"> yes <pause dur="0.5"/> yes </u><pause dur="0.2"/> <u who="sm0193" trans="pause"> then we get a log of one</u><pause dur="0.7"/> <u who="nm0191" trans="pause"> then we get the

logarithm of one <pause dur="0.2"/> </u><u who="sm0193" trans="latching"> yes </u><u who="nm0191" trans="overlap"> which is zero </u><pause dur="0.2"/> <u who="sm0193" trans="pause"> yes and i ask if there is </u><pause dur="1.1"/> <u who="nm0191" trans="pause"> there it is </u><u who="sm0193" trans="overlap"> yes </u><pause dur="1.1"/> <u who="nm0191" trans="pause"> so that corresponds to that </u><u who="sm0193" trans="overlap"> yes </u> <u who="nm0191" trans="latching"> yes sorry i <pause dur="0.3"/> i <shift feature="voice" new="laugh"/> thought <shift feature="voice" new="normal"/> you were asking a different question <pause dur="0.2"/> i beg your pardon <pause dur="2.5"/> okay <pause dur="1.1"/> so this is <pause dur="0.3"/> this data replotted <pause dur="0.7"/> and we see a straight line <pause dur="1.6"/> okay it works for winter barley <pause dur="0.8"/> if you look <pause dur="0.3"/> at <pause dur="0.2"/> the <pause dur="0.6"/> # pictures at the back <pause dur="1.7"/> you'll see <pause dur="0.7"/> that it works <pause dur="0.2"/> for <pause dur="0.3"/> Dutch elm disease <pause dur="2.6"/> and <pause dur="1.1"/> if i take <kinesic desc="changes transparency" iterated="y" dur="7"/> the cocoa swollen shoot example <pause dur="1.6"/> show it in a slightly different way <pause dur="1.9"/> there's our curve <pause dur="0.3"/> running over a period <pause dur="0.7"/> of eight years <pause dur="3.5"/><kinesic desc="puts transparency on top of current transparency" iterated="n"/> if we <pause dur="0.2"/> replot on a logit scale <pause dur="0.7"/> but the same time scale <pause dur="2.1"/> here's the blue line <pause dur="0.6"/> corresponding to the blue axis <pause dur="0.2"/> a logit scale <pause dur="1.3"/> this bendy curve <pause dur="1.1"/> is more or less a straight line <pause dur="0.4"/> not <pause dur="0.8"/> that point is a little bit off at the end <pause dur="0.8"/> but basically over this period <pause dur="0.6"/> it runs as a straight line </u><pause dur="1.8"/><u who="sm0194" trans="pause"> sorry at the logit # axis # zero is the point that the half of the </u><u who="nm0191" trans="overlap"> yes </u><u who="sm0194" trans="overlap"> plants are infected <gap reason="inaudible" extent="1 sec"/> </u><u who="nm0191" trans="overlap"> yes <pause dur="0.6"/> that's right </u><pause dur="0.4"/><u who="sm0194" trans="pause"> okay </u><pause dur="5.3"/> <u who="nm0191" trans="pause"> <kinesic desc="changes top transparency" iterated="y" dur="13"/> and it even works <pause dur="0.3"/> for <pause dur="1.1"/> the phymatotrichum case <pause dur="2.0"/> # <pause dur="0.9"/> if i can get the <pause dur="0.4"/>

axes <pause dur="0.2"/> to overlap <pause dur="0.7"/> again the time scale stays the same <pause dur="0.7"/> but <pause dur="0.9"/> the <pause dur="0.4"/> disease has been replotted on a logit scale <pause dur="0.8"/> and <pause dur="1.9"/> we have a straight line <pause dur="0.4"/> for the first four points <pause dur="0.3"/> and then <pause dur="0.3"/> this one at the end <pause dur="0.3"/> which is decreasing here <pause dur="0.2"/> is quite obviously not on the curve <pause dur="1.2"/> that actually corresponds then <pause dur="0.7"/> here <pause dur="0.3"/> is where something has happened <pause dur="1.4"/> not the sharp increase <pause dur="1.2"/> but at the end <pause dur="0.2"/> something has happened <pause dur="0.3"/> and what happened here of course was that <pause dur="0.4"/> when they reached the situation with eighty per cent of the cotton <pause dur="0.2"/> infected <pause dur="0.4"/> they did something about it <pause dur="1.4"/> wasn't a terribly effective action <pause dur="1.0"/><kinesic desc="writes on board" iterated="y" dur="1"/> but <pause dur="0.8"/> it was perhaps even more effective than they realized <pause dur="0.3"/> in that without that they'd have probably gone to ninety-five per cent <pause dur="1.5"/> okay <pause dur="1.2"/> so by <pause dur="0.6"/> replotting the data you begin to see <pause dur="0.3"/> what's happening <pause dur="1.6"/> cocoa swollen shoot and the final one is <pause dur="1.0"/> phytophthora <pause dur="4.3"/><event desc="looks through transparencies" iterated="y" dur="4"/> that's puccinia striiformis i <trunc>th</trunc> this <pause dur="0.5"/> i seem to want to lose this one don't i <pause dur="0.7"/> here it is <pause dur="1.9"/><kinesic desc="changes top transparency" iterated="y" dur="7"/> yep <pause dur="1.0"/> potato blight <pause dur="0.4"/> the great <pause dur="0.2"/> classic plant disease <pause dur="1.0"/> here we are <pause dur="2.6"/> very different scale of

epidemic <pause dur="0.6"/> but <pause dur="0.2"/> replotted on a logit scale <pause dur="0.6"/> it's a straight line <pause dur="9.7"/> and not only this <pause dur="0.7"/> but <pause dur="0.6"/> we've also now <pause dur="0.4"/> got a way of describing these very diverse diseases <pause dur="1.5"/> in a way which makes it possible to compare what is different about them <pause dur="2.2"/> here's phytophthora infestans <pause dur="1.7"/> the <pause dur="1.1"/> logit <pause dur="0.3"/> rate of increase i'm sorry this isn't <pause dur="0.4"/> terribly distinct <pause dur="0.6"/> owing to <pause dur="0.5"/> having got <pause dur="4.2"/> and that says nought-point-six <pause dur="0.7"/> okay <pause dur="0.9"/> if we <pause dur="0.4"/> go <pause dur="0.4"/> from <pause dur="1.6"/> there to there a span of fifty days <pause dur="1.0"/> the <pause dur="0.2"/> change in the logit amount of disease <pause dur="0.5"/> is <pause dur="0.4"/> minus-two-point-five to nought-point-six <pause dur="0.4"/> which is <pause dur="0.2"/> three-point-one <pause dur="0.9"/> over fifty days <pause dur="0.3"/> so the slope <pause dur="0.7"/> is <pause dur="0.2"/> point-o-six-two <pause dur="0.4"/> per day <pause dur="3.4"/> if we compare that with the phymatotrichum <pause dur="1.6"/> the slope <pause dur="0.6"/> on this one <pause dur="2.4"/> is an increase of five logits <pause dur="0.4"/> over four years <pause dur="0.6"/> sorry i was blocking that <pause dur="0.3"/> an increase of five logits <pause dur="0.9"/> over four years <pause dur="0.8"/> so <pause dur="0.5"/> the rate of increase <pause dur="0.2"/> is <pause dur="0.2"/> one-point-two-five <pause dur="0.4"/> per year <pause dur="3.3"/> far far far slower than the potato blight <pause dur="0.3"/> but just <pause dur="0.5"/> the same pattern <pause dur="3.7"/><kinesic desc="changes transparency" iterated="y" dur="3"/> if we look <pause dur="0.2"/> at <pause dur="1.2"/> the <pause dur="1.5"/> cocoa swollen shoot

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