Lethal and Sub-Lethal Effects of Novaluron (Pedestal®) on the Soil-Dwelling Predatory Mite, Stratiolaelaps scimitus (Womersley) (Acari: Mesostigmata: Laelapidae), under Laboratory Conditions

Abstract

Laboratory experiments were conducted to determine the lethal and sub-lethal effects of the insect growth regulator, novaluron, on Stratiolaelaps scimitus (Womersley), a soil-dwelling predatory mite widely marketed in North America as Hypoaspis miles (Berlese) for biological control of dark-winged fungus gnats (Bradysia spp.). The lethal effects of novaluron and dicofol were determined at 24, 48 and 72 h. Fifty S. scimitus protonymphs were used for each treatment. Novaluron was applied at a concentration of 62 ml per liter and dicofol was applied at 171 mg per liter. In the sublethal effect experiment, 15 S. scimitus protonymphs were exposed to water and novaluron for 72 h. Novaluron did not have any harmful effect on S. scimitus protonymphs (0% mortality) after 72 h of exposure. Dicofol, as the positive control, caused 58, 98 and 100% mortality of S. scimitus protonymphs after 24, 48 and 72 h of exposure, respectively. After 72 h of exposure, novaluron significantly prolonged the duration of the protonymphal stage by 1 to 2 d, compared to the water control. However, after the mites had molted to the deutonymphal stage, no significant effect on the duration of this stage was observed. This study presents new research on the compatibility of the insect growth regulator, novaluron, with a different mite species. As a result, greenhouse producers can use novaluron to manage plant-feeding insects without disrupting biological control programs for fungus gnats.