As the biology of WFT was not fully understood, HDC project SF 80 is investigating the behaviour of the pest in everbearer crops leading to improved integrated control strategies.

WFT is resistant to many pesticides. Currently the most effective is spinosad (Tracer), which can only be applied four times a year to any strawberry crop. This restriction is a resistance management strategy and it is vital to follow it as there has already been a confirmed case in the UK of WFT developing resistance to the insecticide on strawberries.

Results from the project have so far shown that WFT is successfully overwintering in everbearer strawberries both in Kent and Herefordshire. The first WFT adults were detected in early March in flowers of dandelion and groundsel growing in the crop and in the crowns and old foliage of overwintered strawberry plants. This underlines the need for good hygiene in the crop and surrounding area in both summer and winter. In summer, most WFT was found to pupate in the soil directly under plants, with lower numbers pupating in the soil underneath the polythene covering the beds.

The project aims to recommend how to use predators successfully. Amblyseius cucumeris at higher rates than for tarsonemid control may be effective against adult WFT but introduction timing and method are tricky. Biological control agents to target pupae in the ground using a predatory beetle and a parasitic nematode are being tested in commercial crops.