Erythritol, an artificial sweetener, has shown promise as an organic, human-safe insecticide. Recently, erythritol applications were shown to be successful at controlling pear psylla, the key pest of pear in the Pacific Northwest, USA. Through a series of bioassays, we sought to determine if erythritol could also be used for controlling twospotted spider mite and pear rust mite, two other important pear pests. We also examined whether erythritol had acute or sublethal impacts on the beneficial mite, Galendromus occidentalis, through a variety of expsoure methods. We determined that a high concentration of erythritol (30%) had efficacy against both pest mite species and caused arresting behavior in twospotted spider mite. Erythritol caused little acute mortality in G. occidentalis, but did reduce fecundity and prey consumption through some exposure methods. Through motion capture software (Ethovision), we determined that this is primarily due to reduced movement, likely caused by difficulty walking on fresh deposits and excessive grooming behavior. Because the predatory mite non-target effects were less acute than those for the two pest mites, we concluded that erythritol could likely be integrated into pear IPM without disrupting mite biological control.
