Effect of pore size and gap width of artificial oviposition substrates on the egg-laying behavior in Agrilus planipennis: implications for larval host selection

Authors: GREEN, MITCHELL - University Of Massachusetts, Amherst; Duan, Jian

Submitted to: Journal of Insect Behavior
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/7/2025
Publication Date: 7/15/2025
Citation: Green, M., Duan, J.J. 2025. Effect of pore size and gap width of artificial oviposition substrates on the egg-laying behavior in Agrilus planipennis: implications for larval host selection. Journal of Insect Behavior. https://doi.org/10.1007/s10905-025-09883-0.
DOI: https://doi.org/10.1007/s10905-025-09883-0

Interpretive Summary: The emerald ash borer (EAB) is an invasive forest pest that currently threatens North America’s ash resource. Female EAB prefer to lay eggs underneath bark flakes for protection from disturbances such as predators. However, it is not known what sized gaps or crevices female EAB will perceive as optimal to lay eggs under. Here we determined the physical constraints of EAB egg laying behavior. We found that female EAB exhibit preferences for gap or crevice sizes that are neither too tight nor too loose to provide adequate shelter for their eggs. We also found that female EAB could not penetrate 0.04 mm2 mesh pores with their ovipositors. Our findings help to describe behavioral limits of an economically important invasive insect and may help inform management.

Technical Abstract: Many phytophagous insects must select for oviposition sites that maximize the probability that their offspring successfully develop from egg to larvae. Various groups of woodboring insects, such as the invasive emerald ash borer (EAB), Agrilus planipennis Fairmare, tend to select for oviposition sites underneath bark cracks and crevices. Although the oviposition preference for rougher bark has been demonstrated, the exact limits that govern EAB oviposition site selection are unknown. Here we first determined the effective bark gap or crevice size that gravid EAB females would oviposit under through a series of trials with coffee filter paper covered with different pore sizes of mesh screening in a no-choice experiment. We then conducted a choice experiment where we wrapped an ash log with polypropylene ribbons at different degrees of tightness as potential oviposition stimulants. We found that female EAB were able to oviposit onto coffee filter paper through mesh pores (squares) ranging from 0.6 x 0.6 mm2 to 1.4 x 1.4 mm2, but not through mesh with 0.2 x 0.2 mm2 pore sizes in no choice experiments. In the choice experiment, female beetle exhibited a preference for ribbons wrapped with a 0.5 mm gap between ribbon and log over the >1.00 mm and <0.06 mm treatments. These results also closely aligned with the measured width and thickness of 30 female EAB ovipositors. Our findings suggest that female EAB exhibit preferences for gap or crevice sizes that are neither too tight nor too loose to provide adequate shelter for their eggs. These results may have important implications for larval host selection in field settings as the attribute of bark crevices limiting EAB oviposition may vary drastically with host plant and species.