The first spotted-wing drosophila (SWD; Fig 1) was collected June 17th in one of our monitoring trap serviced by Hanna McIntosh for our raspberry mulch study. The traps are located in a raspberry patch at the West Madison Agricultural Research Station. We have been keeping track of the date of first detection for the past 10 years (table below) and it is likely that the high temperatures we have been experiencing in the last couple of weeks slowed down SWD activity and inhibited egg laying and reproduction. More moderate temperatures (70-80F) and humid weather conditions are more conducive to SWD activity and egg laying.
|Date of 1st detection
If you have not done so already, it is strongly recommended for fruit growers that grow strawberry, raspberry, blueberries, cherries, and other soft-skinned fruit to begin monitoring for SWD as soon as possible and to finalize their management plans for SWD. Commercial or homemade traps and baits should be deployed at this time, with one trap per acre and checked at least once or twice a week. Commercial traps and lures can be purchased from companies such as Great Lakes IPM. To make your own trap, use a 32 oz. clear plastic deli cup with a lid, drill or melt 3/16” holes around the top of the cup to allow SWD flies to enter. Traps can be baited with either ~1 inch of apple cider vinegar, or a yeast-sugar mix (1 Tbsp. active dry yeast: 4 Tbsp. sugar: 12 oz. water). Add a couple drops of unscented dish soap to prevent flies from escaping.
Once fruit is ripening and the first fly is caught in any of your traps, you are advised to implement management strategies. For strawberry and grape growers we recommend to sample suspected fruit to look for the presence of larvae (see previous article here). We recommend checking fruit twice a week, crushing the fruit and looking inside for SWD larvae, or using the salt test method.
Once you detect the first fly in a trap or find larvae in your fruit, harvesting fruit every 2 days and bagging culled fruits for 32 hours should be implemented to reduce SWD populations as part of an IPM program. More information about these strategies can be found in this article. Other management methods, such as physical barrier, refrigeration, and chemical control were discussed in our article on organic management of SWD and in this comprehensive organic management publication. Other strategies that can be used in conventional management are also discussed in a previous article.
If you are planning to use chemical control it is important to remember to start applying insecticides when the fruit starts turning color and at least 1 fly has been detected in the patch, and to apply products every 5-7 days until the end of harvest. For organic production, insecticides options rely primarily on Spinosad IRAC 5 (Entrust) as the most efficacious compound. Spinosad should be rotated with either Pyrethrins IRAC 3A (Pyganic), a chromobacterium (Grandevo), azadirachtin combined with pyrethrins IRAC 3A (Azera), or the peptide SpearT for resistance management. Resistance to Spinosad has been reported in SWD populations in some other states and rotating chemistries is critical to delay resistance to the most effective chemistry for organic production.
Conventional insecticides rated excellent for SWD control include Pyrethroids IRAC 3A (e.g., Brigade, Capture, Mustang Maxx, Hero, Danitol), Diamides IRAC 28 (e.g., Exirel, Verdepryn,), Spinosyns IRAC 5 (e.g., Entrust, Delegate), Carbamates IRAC 1A (e.g., Lannate), and organophosphate IRAC 1B (e.g., Malathion, Imidan). Please remember to rotate amongst different classes of insecticides or IRAC groups to prevent insecticide resistance. Please check the labels to make sure the crop you intend to spray is present on the label and refer to the Midwest Fruit Pest Management Guide for more information.
Happy growing season!This article was posted in Insects and tagged Berries, Christelle Guédot, insects, Spotted Wing Drosophila, SWD.