Setting up monitoring traps and starting sampling/sweeping protocols for tarnished plant bug (TPB; Fig 1), Eastern flower thrips (ETF; Fig 2) and two-spotted spider mites (TSSM; Fig 3) should be a priority at this time.

Tarnished plant bugs will start moving into strawberry fields, as soon as plants are blooming and scouting is recommended at least once a week. Monitor with sweep nets for adults and nymphs as both 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.

Insecticides include Brigade and Danitol for pyrethroids and Actara and Assail for neonicotinoids. For organic production, products containing Azadirachtin have shown control in some studies.

Eastern flower thrips can be unpredictable as they move, sometimes in numbers, on air currents from Southern states especially early in the spring, while some may actually overwinter on wheat in Wisconsin. To monitor for EFTs, shake or tap 10 blossoms per site at 10 or more sites per variety in a white bowl or tray. Action thresholds of 2-10 thrips per flower or small berry may warrant a chemical control, depending on your level of tolerance (for more info see previous article on EFT here).

Insecticides for controlling EFT include Brigade and Danitol. These broad spectrum insecticides will also help control other insects such as strawberry clipper. Reduced risk insecticides include Assail and Radiant. For organic production, Entrust can provide control of EFTs.

Two-spotted spider mites (TSSM) can occasionally become a problem in strawberry fields and can be managed with annual renovation of strawberry beds and naturally-occurring predatory mites that can keep two-spotted spider mite populations in check. A ratio of one predatory mite to 10 TSSM should provide adequate biological control. In addition, avoid applying excessive nitrogen fertilization as it may cause TSSM population to build up. Dry conditions are also favorable to mite build up. Finally, pyrethroid insecticides are known to cause mite flare ups and early season insecticide applications can reduce natural enemy populations such as predatory mites, minute pirate bugs (Orius spp.) and lady beetles that will help control mite populations. This emphasizes the need to use the action thresholds outlined above for EFT and TPB to reduce chemical interventions early in the season. For two-spotted spider mite, mite infestations of 25% or more of leaflets sampled (1 or more mites on 15 out of 60 leaflets sampled) will trigger the use of a miticide. Products that have shown excellent control on TSSM include Abamectin (e.g. Agri-Mek), etoxazole (e.g. Zeal), hexythiazox (e.g. Savey), bifenazate (e.g. Acramite), acequinocyl (e.g., Kanemite) and fenpyroximate (e.g. Portal). Assail also provides good control for TSSM. In organic production, oils such as mineral oils and sesame oil have shown good control in some studies.

As always, avoid spraying insecticides during bloom when pollinators are present. If you need to spray during the bloom period, please use reduced risk insecticides and apply pesticides at night to decrease direct exposure to pollinators. There is a great resource from the University of California where you can search by trade name of chemical products and see their toxicity to bees to help you make decisions. Please refer to the Midwest Fruit Pest Management Guide for more pesticide recommendations and, as always, read and follow the labels.

Happy growing season!

This article was posted in Insects and tagged Christelle Guédot, eastern flower thrips, insects, Tarnished Plant Bug, two-spotted spider mites.