Release Strategies and Cultural Modifications for Biological Control of Twospotted Spider Mite by Neosieulus fallacis (Acari: Tetranychidae, Phytoseiidae) on Hops

Biological control of the twospotted spider mite, Tetranychus urticae Koch, on hops, Humulus lupulus L., with the predator Neoseiulus fallacis (Garman) was explored to understand the factors important in successful T. urticae management. The timing of introductions of N. fallacis , the height of release on the plant, overwinter survival, and cultural factors were investigated to determine the optimal use patterns for this predator. Release height seemed to be unimportant, but release timing was influential when there were unusually low or high T. urticae densities. N. fallacis overwinters in hop fields, but early spring cultural practices inhibit survival to summer. Three cultural practices, all for reduction of foliar growth, were found to be detrimental to biological control. Predators released into 0.25-ha plots in commercial fields maintained T. urticae to commercially acceptable levels throughout the season. A provisional management protocol is described for biological control of T. urticae with N. fallacis .