What a shock! After spending so much time caring and growing your berry plants, just as you pick those ripe berries, you notice small white worms. Disgusted. Do not just leave it there…
The spotted wing drosophila is a “vinegar fly” or “small fruit fly” which is known to be a fruit killing machine. These flies primarily attack raspberries, blackberries, blueberries, strawberries, and wine grapes. The adults have a yellowish-brown colour with dark coloured bands on the abdomen as they grow to about 2-3mm. The larvae is white with a cylindrical body which tapers to one side.
The adult spotted wing drosophila inserts their eggs into soft fruit where the larvae will develop. The female has a special egg-laying organ, serrated like a saw, in order to lay her eggs inside ripening fruit. The white legless larvae then leave the fruit and later emerge as adults. These flies can complete an entire lifecycle in as little as 7 days. The larvae feed within the healthy ripening fruit which causes the brown sunken areas on the berries. If the fruit have fallen to the ground the larvae will pupate in the soil. Due to the fact that the larvae lives inside the fruit or even soil, this causes a huge threat, as it protects them from insecticides making it even more difficult to control them.
How to control the spread of the spotted wing drosophila;
Control of the spotted wing drosophila is difficult as sanitation is the most practical solution. Spiders and ants do eat the spotted wing drosophila larvae and pupae on the fallen berries. Other natural predatory insects include the ladybug and the lacewing.
Ensure to pick the berries when they are ripe and try not to leave the ripened fruit on the plants. A good idea would be to the pick the berries just before they ripen and store them in the fridge/freezer as they will ripen within another day. The rotting fruit will attract the flies, so finding a way to dispose them where flies will not be able to emerge and reinfest, is the best option. Prune your plants regularly as this will increase the amount of sunlight and reduce humidity. (Prune the dead branches which have already had fruit, as this will make way for new branches to sprout.) Cooling the fruit for 3 days will kill the larvae of the spotted wing drosophila.
Spray an insecticide immediately, early in the morning or late afternoon, as this is when the spotted wing drosophila is most active. Organic insecticides have shown very little effect against the dreaded spotted wing drosophila. Neem oil is known to kill aphids, mealybugs, mites, Japanese beatles, whiteflies, larvae and scale seeing that it is organic and wont harm beneficial insects such as bees and ladybugs. If you decide to use an insecticide, choose one with a short preharvest waiting period.
Adding netting with at lease 1mm mesh holes will surely help to prevent the spotted wing drosophila from gaining entry to the ripening fruit.
Once you have noticed any infestation it is best to treat and regularly check your fruit, as the spotted wing drosophila is highly aggressive, prolific, invasive and have been known to completely destroy late berry crops.