Beet leafhopper and spider mites management in industrial hemp in Northeastern Oregon

Hemp (Cannabis sativa L.) is considered a high-value crop and is quickly becoming well established in the US Pacific Northwest. Hemp production and market focus on medicinal products, fiber, and oilseed. Fiber and oilseed/grain hemp are collectively known as industrial hemp. Northeastern Oregon represents a growing region in terms of industrial hemp per hectare production. Several species of arthropod pests affect hemp in Oregon, including beet leafhopper Circulifer tenellus Baker (Hemiptera: Cicadellidae) and spider mites Tetranychus spp. (Acari: Tetranychidae). Spider mites cause direct feeding damage, while beet leafhoppers are a known vector of Beet Curly Top Virus, an emerging hemp disease. To evaluate effective control options for beet leafhoppers and mites, we evaluated in a greenhouse trial the effects of four organic active ingredients: Chromobacterium subtsugae, Burkholderia spp., Chenopodium ambrosioides, and 1.2% Azadirachtin, plus an untreated control. Insecticides were applied using a calibrated hand sprayer on foliage when plants reached 40 cm height. In two separate experiments, five beet leafhoppers per plant and ten spider mites per plant were placed in clip cages placed on plants 1 hour after treatment. Mortality was assessed at 1, 3, and 7 DAT (days after treatment). Data collected were subjected to an ANOVA and results were reported as a percentage of mortality. In general, applications made with Burkholderia spp. provided greater mortality rates against beet leafhoppers when compared to other treatments. For mites, at 7 DAT, all organic compounds caused mortality with no statistical differences except for the untreated control.