Future crop protection: Precision application of biopesticides

Secondary Supervisor(s): Mr Emilio Loo Monardez

University of Registration: University of Warwick

BBSRC Strategic Research Priority: Sustainable Agriculture and Food (Plant and Crop Science)

Project Outline

Crop pests are a major constraint on agricultural production, resulting in significant losses of yield and crop quality. For over 50 years, crop protection has been based around the use of synthetic chemical pesticides, but the number of products approved for use is declining markedly because of concerns about human and environmental safety, as well as control failures because of the evolution of heritable resistance in target pests.

These changes are creating a market demand for bio-based alternatives in the EU, which are safer and more environmentally benign than ‘old’ synthetic chemistries. Biopesticides (aka bioprotectants) are plant protection products based on living microorganism or natural products that can be used as alternatives to synthetic chemical pesticides as part of Integrated Pest Management. The bio-based industry for crop protection represents a new, dynamic and rapidly evolving sector with significant potential to contribute to sustainable agriculture.

The change in the policy environment in Europe has had a positive impact on the outlook for biopesticides. In the last decade, they have increased from 2.5% of the EU total pesticides market to 8% today, but uptake by farmers and growers is not high enough to fill the gap being created by the loss of conventional chemical pesticides.

One of the key barriers to uptake is that biopesticides are largely contact acting and they have a lower intrinsic potency than conventional toxicant synthetic pesticides, which means that they require very good spray application to deliver an effective dose to the target (in contrast, farmers can often get away with poor application of synthetic pesticides as these have high potency and many have systemic or translaminar activity, meaning the target does not have to be contacted directly for the pesticide to have an effect). Our previous work has shown that biopesticide application in commercial practice is often suboptimal and, therefore, there is a need to develop precision application systems. New advances in sensor technologies, vision systems, robotics, digital, and AI all have potential to revolutionise the performance of biopesticides through early pest detection, autonomous spray systems, and accurate delivery to the target. This should include a switch to low volume and ultra-low volume application systems, which are more efficient and much less wasteful than traditional high-volume systems.

In this project, we will investigate precision application for biopesticides using our specialised facilities at Warwick Crop Centre. We will use 2 pest systems - spider mites (which are pests of a wide range of protected crops), and aphid and lepidopteran pests of field brassica crops – treated with biopesticides based on insect pathogenic fungi, bacteria, and ‘botanicals’ (plant extracts with pest activity). In the first part of the project, we will use our track sprayer facility at Wellesbourne to quantify how key spray application variables determine the actual dose of biopesticide received at the plant surface for a nominal constant dose application, and then relate this to the amount of pest control recorded in laboratory bioassays. This information will be used to determine the optimum spray application parameters, particularly for low volume and ultra-low volume systems. In the second part of the project, we will translate these findings to our ASPA robot testbed (an autonomous vehicle with an AI vision system and deltabot arms for pesticide spray application). The ASPA AI will be trained to identify and phenotype vegetable brassicas as a representative row crop. Robot precision spray application to the crop will then be quantified with biopesticides and performance compared against a conventional broadcast spray. Our ambition is that this work will open the door for the use of precision application with robot sprayers for biopesticides, which will facilitate the wider uptake of biopesticides by farmers and growers and also provide a boost for the use of new agri-technologies for sustainable food production.

References

Glare, Travis et al. (2012). Have biopesticides come of age? Trends in Biotechnology, 30, , 250 - 258.

Hothouse Flowers: understanding how climate change is causing yield loss in UK protected crop production

Secondary Supervisor(s): Dr Florian Busch, Dr Scott Hayward, Mr Emilio Loo Monardez

University of Registration: University of Warwick

BBSRC Strategic Research Priority: Sustainable Agriculture and Food (Plant and Crop Science)

Project Outline

Commercial greenhouses provide a significant part of the fresh produce (fruit and vegetables) consumed in the UK. Unfortunately, this production is now facing severe threats from climate change, including from high temperatures that occur during summer heatwaves. UK greenhouse food production (valued at £120M p.a.) is particularly vulnerable to climate change as the country is predicted a 30% increase in extreme heat days by 2050, one of the largest rises in the world. Summer heat waves that raise glasshouse temperatures above the optimum for plant growth and cause significant, irreparable damage and yield loss. The problem is that plant physiological processes start to fail over narrow thermal windows at elevated temperatures, and so tipping points resulting in crop damage happen very quickly under heat stress.

Pilot research at Warwick on the mechanism of heat damage in tomato crops showed that a simulated heat wave inhibited pollen synthesis in immature tomato flower buds which prevented subsequent pollination & fruit development. The literature indicates that pollen susceptibility to heat stress is common and other economically important greenhouse crops are susceptible. However, the temperature and exposure time thresholds are yet to be determined. Other important indicators of plant health under heat stress, e.g. photosynthesis have also not yet been studied.

Greenhouse systems can regulate high temperatures to some extent, but cooling needs to be employed efficiently to limit costs. At the moment, growers visually inspect their crops to monitor for heat damage, but they lack skilled staff to do it properly, and the problem is usually detected too late. The way forward is to develop physiological models of heat damage so that we understand the threshold conditions for damage to occur, and link these to within-crop temperature sensors that can act as a warning system.

The aim of this project is to understand in detail how elevated temperatures cause damage to pollen production in tomato varieties. Tomato plants will be grown in controlled environment chambers under simulated commercial growing conditions and then subject to periods of heat stress. Leaf scale gas exchange will be used to determine effects of heat stress on CO₂ uptake over time. Gas exchange data will be correlated with leaf temperature and multispectral reflectance as a model of plant stress. We will use a range of treatments including (i) constant elevated daytime temperature; (ii) daytime temperature cycle that mimics a glasshouse heat wave; (iii) short pulse of heat stress followed by recovery. This will be followed by work to quantify the rate of individual flower development from the immature bud stage to anthesis and collecting pollen samples for analysis to quantify effects of elevated temperature vs. pollen abundance & viability. The findings will then be translated into commercial glasshouse crops, where we will record bud, leaf and ambient temperatures during summer hot periods, combined with crop multispectral imaging, and follow the development of the plants to include analysis of pollen density and viability from the mature flowers. The eventual aim is to develop an AI “self-learned” models based on variables from the physiology model and the real-time data collected from autonomous monitoring systems to predict and mitigate crop damage risks. Long-term, the systems developed in the project could also be used to screen germplasm collections to identify plant varieties that are able to develop well under heat wave conditions and which could be put into crop genetic improvement programmes.

References

Zahra et al (2023) Plant photosynthesis under heat stress. Environmental and Experimental Botany, 206, 105178.

Paupiere et al (2017). Screening for pollen tolerance to high temperatures in tomato. Euphytica, 213, 10.1007/s10681-017-1927-z.

Investigating the effect of climate heating on bumblebees used for commercial pollination of protected crops

Secondary Supervisor(s): Dr Florian Busch, Dr Scott Hayward, Mr Emilio Loo Monardez

University of Registration: University of Warwick

BBSRC Strategic Research Priority: Sustainable Agriculture and Food (Plant and Crop Science)

Project Outline

To meet food demand in the UK (and globally) many commercial growers of fruit and veg must use greenhouse systems to optimise growing conditions and pest control. The production of high value protected crops, such as tomato, pepper, aubergine and strawberry, is reliant upon biological pollination using managed bumblebees (Bombus terrestris). Specialist agronomy companies have developed ways to mass produce bumblebee nests under carefully controlled conditions, and these are then supplied to growers to pollinate their crops. In recent years, however, issues around pollination failure have become increasingly common, associated with high temperatures caused by climate change. Unfortunately, climate change is resulting in an ever-increasing frequency of heat wave events, causing significant crop damage and reduced pollinator activity. This undermines UK food security, e.g. recent declines in tomato yield of up to 20%.

Heat damage occurs very rapidly once certain physiological thresholds of heat stress are reached, but these temperature (and time) thresholds remain unknown for most crop and pollinator species. Global warming means this problem is going to increasingly impact global food production and it is essential for commercial growers to identify economically viable solutions.

This project will investigate the effect of heat stress using tomato crops and their associated bumble bee pollination systems, focusing on bee movement, behaviour and colony health. Our vision is to exploit advances in digital technology and new biological understanding to make production more sustainable and resilient. By understanding the effects of greenhouse environmental conditions of bee activity, we will be able to develop mitigations that enable pollination and crop production under climate change conditions. As part of this, we will compare two different subspecies of bumblebee, Bombus terrestris audax (Bta), which is native to Great Britain and is used by British growers for crop pollination, and Bombus terrestris dalmatinus (Btd), which originates in southern Europe and which we may predict will perform better in greenhouse conditions. Btd was used successfully for nearly 30 years in UK greenhouse crops, but its use was severely restricted in 2015 following a government agency review, and growers were required to switch to Bta. Growers reported ongoing issues with pollination after the switch to Bta. Bumblebees regulate the temperature within their nests by generating body heat when it is cold, and by wing fanning when it is too hot. It is particularly important for them to keep the nest temperature stable to rear and protect the bee brood. Pollinator performance is known to decline markedly under heat stress but is poorly understood for Bta and Btd. Previous work has shown clear differences in the low temperature biology of these subspecies, so we hypothesize differential performance under heat stress.

There are two main work objectives. Firstly, laboratory research will be done to characterise the thermal biology of both Bta and Btd. Brood fanning behaviour will be investigated using individual worker bees in test arenas containing a beeswax ‘brood dummy’ (which elicits fanning behaviour). Temperature will be raised at different rates from 20 - 35°C. Bees will be video recorded, and the threshold temperature for wing fanning, and the % of bees that fan, will be quantified. The thermal limits of coordinated movement, critical thermal maximum, (CTmax) will be assess following standard methods. Experiments will also be done using the whole colony, with video analysis to evaluate how behaviour changes with heating. Secondly, bee traffic rates will be quantified within a commercial tomato crop during ‘standard’ conditions and also when summer heat waves are occurring. RFID tags and camera traps will be used to quantify flight traffic rate, flight duration & drifting from Bta vs Btd hives placed in the same crop. We will record temperature within the hives as well as leaf & ambient temperature. The aim is to include naturally occurring periods of high temperature (c. 30°C) as well as lower, standard temperatures (20 - 25°C). The hypothesis is that above the temperature threshold for brood fanning, Bta traffic /pollination activity will rapidly decline with increasing temperature. If time permits, we will test mitigations, e.g. focused forced air cooling, to lower hive temperatures.

References

Chandler et al (2019). Are there risks to wild European bumble bees from using commercial stocks of domesticated Bombus terrestris for crop pollination? J Apicult Res 587,1-17.

Bretzlaff et al (2024) Handling heatwaves: balancing thermoregulation, foraging and bumblebee colony success. Conservation Physiology, 12, doi: 10.1093/conphys/coae006.

Owen, Bale & Hayward (2013) Can winter-active bumblebees survive the cold? PLoS ONE 8: e80061.

Investigating biopesticides for the control of diamondback moth within Integrated Pest Management

Secondary Supervisor(s): Dr Lauren Chappell, Dr Graham Teakle

University of Registration: University of Warwick

BBSRC Strategic Research Priority: Sustainable Agriculture and Food (Plant and Crop Science)

Project Outline

The diamondback moth (DBM) Plutella xylostella is a brassica-feeding specialist and one of the most important pests worldwide, causing US$5 billion crop losses globally p.a. DBM has evolved resistance to most of the available chemical pesticides used against it. This is causing major problems, particularly in developing countries where, in addition to crop losses, smallholder farmers - normally with inadequate PPE - are forced to use ever more frequent applications of toxicant pesticides with their associated health risks. Therefore, there is an urgent need for new DBM treatments and sustainable systems for using them. Most experts see Integrated Pest Management (IPM) as the way forward. IPM is a systems approach that combines different crop protection practices with careful monitoring of pests and natural enemies. Biocontrol with natural enemies is particularly important for DBM given its propensity to develop pesticide resistance. This should include biopesticides (aka bioprotectants), which are plant protection products based on living microorganism or natural products that can be used as alternatives to synthetic chemical pesticides as part of IPM. Sustainable pest management will need to be based on integrating different crop protection methods rather than relying in a single ‘silver bullet’ approach. However, there is currently a poor understanding of how different crop protection tools interact.

In our research at Warwick Crop Centre, we are working on the components for a new, safe, biologically-based IPM system of DBM, including candidate Brassica accessions with partial resistance to DBM larvae and strains of insect pathogenic fungi (Beauveria bassiana and Metarhizium spp.) that can be used as biopesticides. There are other potential biopesticides that also require investigation, including the bacterial agent Bacillus thuringiensis Bt, plant-derived agents (botanicals such as neem) and physically acting agents such as organic soaps. The aim of this project is to evaluate new biopesticides against DBM and develop an IPM system for using them. The first part of the project will characterise the potency of candidate agents against different DBM life stages in laboratory bioassays (measuring speed of kill, lethal dose, and any sublethal effects on insect development time and fecundity). Work will then be done using our track sprayer facility to optimise delivery of agents to the target, so that they can be used as part of a precision application system. This will be followed by experiments to investigate novel approaches to identify synergies between different biopesticide agents when used concurrently (for example, we have shown previously that Bt can act as a potentiator by slowing down the development of DBM larvae and making them more susceptible to contact acting agents such as Beauveria) or consecutively, informed by models of DBM population growth. Finally, selected agents will be combined with host plant resistance, to test hypotheses about how the host plant mediates the effect of biopesticide combinations on insect survival and population development. The aim is to pioneer a new, safe and sustainable approach to managing DBM that will be applicable in many parts of the world to help food security.

References

Furlong, M. J. et al. (2013). Diamondback Moth Ecology and Management: Problems, Progress, and Prospects. Annual Review of Entomology, 58, 517-541.