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Two miticides recently received registration for use against twospotted spider mites in soybean

by Robert Koch (Extension Entomologist) and Bruce Potter (IPM Specialist)

Growers now have access to two more miticides for use against twospotted spider mites in soybean. These miticides are Agri-Mek SC (Syngenta) and Zeal SC (Valent). These are welcomed additions to the limited suite of chemicals for management of twospotted spider mites in soybean.  They represent insecticide groups (modes of action) not used for soybean aphid.

Agri-Mek SC contains the chemical abamectin (group 6: Chloride channel activators). Zeal SC contains the chemical etoxazole (group 10: mite growth inhibitors). Previously, management of twospotted spider mites relied on the pyrethroid insecticide bifenthrin (group 3: sodium channel modulators) and the organophosphate insecticides chlorpyrifos and dimethoate (group 1: acetylcholinesterase inhibitors).  Unlike bifenthrin and chlorpyrifos, abamectin and etoxazole have activity on mite eggs.  Supplemental labels for Agri-Mek SC and Zeal SC are (or should soon be) available on the websites for these companies.

As aphid scouting continues this year, keep an eye open for twospotted spider mites, particularly in dry areas. Historically, twospotted spider mites have only been problematic in soybean under drought conditions. However, in recent years, we have seen severe infestations develop under conditions with adequate moisture. Recommendations for scouting and management (including a threshold) for this pest can be found in Managing spider mite on soybeans. Keep in mind that applications of some insecticides (e.g., most pyrethroids) for soybean aphid management could flare mite populations, depending on environmental conditions. Always follow instructions on pesticide labels.

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