Augmentation and conservation biological control of Tetranychus urticae on hops in Ohio

The twospotted spider mite, Tetranychus urticae Koch (Acari: Tetranychidae), is a key pest on hops grown in the Midwestern USA, where hop production is a new industry, and little research has been done on the management of T. urticae.  In 2016 and 2017, we conducted an experiment to determine the efficacy of augmentative biological control of T. urticae populations on the cultivar ‘Cascade’ at four hop yards.  In both years, treatments compared Neoseiulus fallacis Garman (Acari: Phytoseiidae), released at a high rate and a low rate, and an untreated control, with eight replicates in 2016 and 17 replicates in 2017.  Additional treatments in 2016 evaluated Galendromus occidentalis Nesbitt (Acari: Phytoseiidae) released at a high and a low rate. The target low rate in both years was one predator per ten T. urticae. The target high rate was one predator per five T. urticae in 2016, and one predator per two T. urticae in 2017.  When weekly monitoring showed that the population reached an ac...