D3412: Emerald ash borer (Agrilus planipennis) oviposition behavior in response to physical environment

The emerald ash borer (EAB) (Agrilus planipennis Fairmare) is an invasive pest that has led to the death of hundreds of millions of ash (Fraxinus spp.) trees in North America. Similar to other Agrlius species, EAB oviposits underneath bark cracks and crevices, presumably to provide shelter from biotic and abiotic factors. However, the exact ranges of crevice size that EAB oviposits under is not known. We sought to quantify this through a series of lab experiments aimed at providing fundamental insights to EAB oviposition behavior. Using standard rearing methods we found that EAB is able to oviposit underneath mesh with pores ranging from 0.6-1.4 mm wide but not under mesh with a 0.16 mm pore size. We then dissected and measured 30 ovipositors from female EAB and found a mean ovipositor width of 0.486 mm (range: 0.270-0.689 mm) and a mean ovipositor thickness of 0.133 mm (range: 0.050-0.291 mm). In another experiment, we wrapped yellow curling ribbons around 20 cm long ash bolts at four tightness treatments (0.06 mm, 0.25 mm, 0.5 mm, and 1.00 mm) that represented artificial bark gap sizes. We presented the logs to gravid EAB females as an oviposition substrate and found greater oviposition under 0.5 mm ribbons, possibly because they were sensed as offering superior protection because they were neither too tight or loose. The results of these assays demonstrate preferential oviposition behavior that corresponds with ovipositor size and may help guide efforts using novel oviposition traps.