An Environmental Model for Developing Novel IPM Techniques for Control of Swede Midge in Brassicas

There were 27,420 ha of horticultural brassicas grown in the UK in 2020, worth £302 million to the UK economy (Defra horticulture statistics, 2020). Swede midge has become a devastating threat to UK brassica production in recent years, since the loss of the insecticide chlorpyrifos. Larval feeding is particularly threatening to headed crops like cauliflower, broccoli and cabbage. It is not possible to grow some of these crops organically anymore because of the midge. Use of crop mesh covers can reduce swede midge damage by excluding the adult midges and thus prevent egg laying but research is needed to use these more effectively and better understand the crop risks, especially as they are often removed for mechanical weeding. Current advice is to rely on rotation and distance from previously infested crops to prevent colonisation of the first-generation midge adults when they emerge from overwintered larvae and pupae in the soil. However, infestations have been found in fields located 20 miles from the nearest brassica crop on land that had not previously grown brassicas for 7-8 years. This behaviour makes it difficult to develop novel control strategies and is worthy of research.

This project proposes to develop an environmental model using GIS to understand how landscape and crop history factors influence pest pressure of the first and second generations of swede midge. The environmental model will be useful to conventional and organic brassica growers alike to help inform crop protection decision making and planning. The project will also assess swede midge pest pressure with the use of mesh crop covers, taking into account crop history and landscape features to determine whether the midges are emerging from the soil in the current brassica field or flying into the crop from another source. The results of this project will help to design effective novel agroecological control strategies based on knowledge of swede midge biology and behaviour, such as trap cropping or use of suppressive cover crops.