Spotted-Wing Drosophila Behaviour: Haygrove Chrysalis' approach to Integrated Pest Management.

Spotted-wing drosophila Drosophila suzukii (SWD) is an invasive vinegar fly originating from Asia, which is now established in Europe, the Americas, and North Africa. SWD females have evolved a characteristic trait allowing them to lay eggs in fruit before other vinegar fly species, overcoming competition for larval resources; a saw-like, serrated ovipositor enables them to pierce the flesh of ripening to ripe fruit and lay eggs. This trait is absent or much less pronounced in most other vinegar flies, which lay eggs in over-ripe to rotten fruit that is softer or damaged and presenting suitable apertures.

The favoured hosts of SWD are berries, particularly raspberries and blackberries. Damage incurs during oviposition, when the fruit surface is pierced creating a gateway for pathogens, and subsequently from the feeding of the larvae within the fruit flesh. Produce affected with SWD is at risk of rejection or rendered unmarketable from larval feeding. The pest status of SWD is exacerbated by its rapid life cycle (egg to adult in 13-14 days at 22°C) and overlapping generations, which culminate in late July to October in the UK growing season with populations reaching several thousand individuals per week in single vinegar-wine baited bucket traps.

Chemical control is essential for SWD, but limited in the range of available active ingredients and the extent of their use, whereas biological alternatives are few or unavailable; cultural control, therefore, plays a big role in SWD management. As a further option, Haygrove Chrysalis offers to study the egg maturation status of female SWD to understand when eggs are fully developed and ready to be laid in fruit. This service aims to assist growers in understanding how to implement and modulate SWD management practices in Spring and Autumn, as part of a comprehensive integrated management strategy for SWD.

Please get in touch with Marco Corradi , Haygrove Chrysalis Entomologist, or visit our website for further information and costings.