A chemical and overwintering honey bee apiary field study comparing new and expired amitraz miticide

(1) Tower Hill School, Wilmington, Delaware, (2) University of California San Diego, La Jolla, California, (3) Denison University, Granville, Ohio

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The ectoparasitic mite Varroa destructor is a significant driver of colony collapse in Apis mellifera, the European honey bee. A. mellifera is a keystone species that serves an essential role in pollination, particularly for large-scale agriculture. Apiculturists commonly combat V. destructor through synthetic acaricides such as amitraz, sold commercially as Apivar® strips. Issues with Apivar strips include their limited shelf life, costliness, and burden to the environment from disposal of unused strips. The purpose of our research was twofold: to determine the difference in levels of amitraz content in plastic Apivar strips from different years and to determine the overwintering success of amitraz-treated hives compared to hives treated with expired amitraz. We expected the amount of amitraz to be significantly reduced in older and expired strips. We extracted amitraz from Apivar strips using chloroform and quantified the concentration of amitraz using high performance liquid chromatography. We also expected that if expired amitraz strips were used to control for V. destructor then overwinter survivorship of the honey bee colonies would be significantly reduced. Our findings reveal that there was no statistical difference in the microgram (µg) amount of amitraz in Apivar strips and that expired Apivar does not impact overwintering survivorship. This demonstrates that the shelf life of amitraz is at least 36 months, in contrast to the 24-month expiration label on the product. Our data shows that using expired Apivar may be an economically viable and environmentally-friendly option for beekeepers.

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