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Cabbage root fly forecast 2024

The forecast outputs below are based on weather data provided by Agrii. The forecasts predict the timing of fly activity. They do not predict the number of insects present in the crop, as this depends on the size of the local fly population. For control purposes, we consider that the pest has become active when 10% of the insects have emerged/laid eggs and that the peak of activity has occurred when 50% have emerged/laid eggs. The predictions will change over time depending on weather conditions.

Late-emerging cabbage root flies

The forecasts in the table below are for ‘early-emerging’ cabbage root flies. There are some areas of the UK where a proportion of the cabbage root flies emerge later in the spring than would be expected. We call these ‘late emerging’ flies and they are genetically different from ‘early-emerging’ flies. Relatively large numbers of late-emerging flies occur in some parts of Devon and south-west Lancashire.

Early-emerging flies - updated 13 June

Location

First generation

10% emergence

First generation

10% eggs

First generation

50% eggs

Second generation

10% emergence

Second generation

10% eggs

Cornwall - Hayle

21 Feb 21 Mar 21 Apr 17 Jun 28 Jun

Kent - Sandwich

5 Mar 30 Mar 25 Apr 7 Jun 19 Jun

Suffolk - Ipswich

27 Mar 11 Apr 5 May 9 Jun 20 Jun

Warwick, Wellesbourne

1 Mar 2 Apr 30 Apr 11 Jun 22 Jun

Norfolk, Norwich

10 Mar 5 Apr 30 Apr 20 Jun 1 July

Lincolnshire - Holbeach

14 Mar 7 Apr 1 May 18 Jun 28 Jun

Nottingham - Stubton

12 Mar 5 Apr 3 May 17 Jun 27 Jun

Lancashire, Southport

12 Mar 7 Apr 4 May 24 Jun 4 July

Yorkshire, York

20 Mar 12 Apr 6 May 17 Jun 27 Jun

Perthshire, Scotland

26 Apr 10 May 23 May 7 Jul 17 Jul

Second generation

10% emergence