First Spotted-Wing Drosophila Detected and Tarnished Plant Bug Populations Increasing

The first spotted-wing drosophila (SWD; Fig 1) was collected June 9th in one of our monitoring trap serviced by Hanna McIntosh for our mulch study. The traps are located in a raspberry patch at the West Madison Agricultural Research Station. Other traps that were targeting overwintering SWD in raspberry and woodlots did not yet catch any SWD. Looking at the date of first detection for the past 9 years (table below), it is recommended to start monitoring in late May to early June and to be ready to implement a management program as early as the first week of June.
Year | Date of 1st detection |
2013 | June 24 |
2014 | June 30 |
2015 | July 8 |
2016 | June 10 |
2017 | June 5 |
2018 | June 1 |
2019 | June 19 |
2020 | June 19 |
2021 | June 9 |
If you have not done so already, I strongly recommend to berry growers that grow strawberry, raspberry, blueberries, and other soft fruits such as cherries 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 plan. 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 sole compound with excellent efficacy. Spinosad should be rotated with either Pyrethrins IRAC 3A (Pyganic), a chromobacterium (Grandevo), or azadirachtin combined with pyrethrins IRAC 3A (Azera) for resistance management. Resistance to Spinosad has been reported in SWD populations in California 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), Spinosyns IRAC 5 (e.g., Entrust, Delegate), and organophosphate IRAC 1B (e.g., Malathion). Please remember to rotate amongst different classes of insecticides or IRAC groups to prevent insecticide resistance. More insecticides are available for SWD control and not all are registered on all small fruit crops, so 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.

Tarnished plant bugs (TPB) have been present at all of our sites in and around Dane county strawberry fields for the last week or so now and populations of adults have been increasing. Plants are in the mixed stage of bloom and small fruits, and sampling for nymphs and adults should happen at least once a week. Both adults and nymphs will feed on strawberry plants and can cause damage. The action threshold for implementing chemical control is 4 adults per 20 sweeps or 1 nymph in 4 flower clusters. In conventional production, insecticides include Brigade and Danitol for pyrethroids and Actara and Assail for neonicotinoids. In organic production, Pyganic (pyrethrins), Aza-direct (azadirachtin) and Grandevo (chromobacterium) have shown good efficacy against TPB. Please refer to the Midwest Fruit Pest Management Guide for more insecticide recommendations. More info on TPB can also be found in this previous article.
Happy growing season!
This article was posted in Insects and tagged Berries, Christelle Guédot, insects, Spotted Wing Drosophila, SWD, Tarnished Plant Bug.