Spotted wing drosophila (SWD) pressure has been low so far this season due to colder conditions than expected for the time of year.
However, as warm temperatures are likely as the season develops it will be important to stay alert to a possible increase in SWD pressure.
Implementation of an integrated pest management (IPM) strategy will be crucial to reduce the risk of SWD damage.
Use the ‘degree day’ model to understand when SWD activity is likely to be high, and action needed.
SWD prefer humid conditions with moderate temperatures, between 15-25°C, so once temperatures reach this level and are sustained for nine ‘degree days’, the pest becomes active and starts to lay eggs within the fruit.
At this point action should be taken, as once the larvae hatch they create brown sunken areas which can result in collapse of the fruit, rendering it unsaleable.
Adult fly populations can be monitored using bait traps containing sweet mixtures, such as apple cider vinegar.
Make sure to change traps at least once a week to increase the chance of successful pest capture.
Maintaining crop hygiene is crucial. Remove all old or damaged fruit, ensuring all the fruit is picked as crop remnants are the perfect habitat for SWD.
If pests are detected, insecticides, such as Spruzit, can be applied to help knock down adults and block the breathing tubes of the larvae and eggs.
Because of its low persistence in the environment, Spruzit fits well into IPM strategies as an alternative to synthetic pyrethroids, which are well known for disrupting biological control agents such as Encarsia formosa, and causing pest resurgence.
For more information on SWD control, please don’t hesitate to contact us, or visit AHDB Horticulture.