Effects of age and feeding on lipid content and flight capacity of Agrilus planipennis

The emerald ash borer, Agrilus planipennis Fairmaire, EAB, is an invasive beetle from Asia that was first detected in Michigan in 2002 and had spread to Minnesota by 2009. Larvae of A. planipennis overwinter in the outer sapwood of ash (Fraxinus spp.) trees where they can experience durations below 0⁰C. To prevent freezing, larvae metabolize lipids to release glycerol into their hemolymph. Pre-pupae do not feed to replenish lipids before completing pupation. Adults feed on ash leaves before dispersal and mating, perhaps to replenish lipids lost during winter.  This study had three objectives: (i) to measure differences in lipid levels from newly-emerged adults that had experienced different winter severity; (ii) to quantify changes in lipid content as adults fed; and (iii) to evaluate the relationship between lipid levels and flight capacity. Adult A. planipennis were reared from green ash collected in Ramsey and Winona Counties, MN.  Adults were assigned treatments and individually placed in cages and provided fresh, lab grown ash (Fraxinus uhdei) leaves to feed on for a set number of days before being flash frozen or flown on a custom flight mill for 24 hours under constant light. Ash leaves were weighed before and after EAB feeding, as well as digitally scanned to quantify total weight and surface area consumed by beetles. After feeding assays and flight tests, EAB were subjected to lipid extraction using petroleum ether. Feeding treatments were compared for weight and lipid gain, flight velocity and total distance flown.