Effects of Selected Biopesticides on Two Arthropod Pests of Cannabis sativa L. in Northeastern Oregon

Hemp (Cannabis sativa L.) cultivation in the United States has expanded rapidly over the past decade. Due to federal and state regulations, only a limited number of studies have examined the chemical options available for controlling pests on C. sativa. In the U.S., two of the most important species of arthropod pests affecting C. sativa are the beet leafhopper Circulifer tenellus Baker (Hemiptera: Cicadellidae) and the two-spotted spider mite Tetranychus urticae Koch (Acari: Tetranychidae). This study evaluated the effects of four biopesticides, Chromobacterium subtsugae, Burkholderia spp., Chenopodium ambrosioides, and azadirachtin, under greenhouse conditions against C. tenellus adults and nymphs and T. urticae adults. Biopesticides were applied to foliage using a calibrated hand sprayer. To evaluate the biopesticides’ potency, C. tenellus adults, nymphs, and mites were released 1 h after treatment; to evaluate the residual efficacy, they were released 7 days after treatment (DAT). In both experiments, C. tenellus adults, nymphs, and mites were counted 1, 3, and 7 days after release. Our results indicate that Burkholderia spp. exhibited the highest efficacy against C. tenellus adults at 7 DAT, whereas C. ambrosioides and azadirachtin caused the greatest nymphal mortality at 1 and 3 DAT, respectively. Our results show that Burkholderia spp. had the greatest potency against C. tenellus adults 7 DAT, while C. ambrosioides and azadirachtin highly affect the mortality of nymphs at 1 and 3 DAT, respectively. Treatments with C. subtsugae and C. ambrosioides showed high potency against T. urticae. Finally, C. subtsugae showed the lowest residual effect against the mite pest. The data presented in this article will add to the arsenal of information to improve the current management strategies used against these two hemp pests.