Impacts of local and landscape characteristics on asparagus beetle populations

Asparagus beetles (Crioceris asparagi, Coleoptera: Chrysomelidae) are one of the key pests of asparagus in Michigan. Although this specialist insect can cause significant economic losses for the asparagus industry, few studies have been conducted to understand their overwintering biology. Growers have observed beetle populations overwintering within and surrounding asparagus fields in decaying asparagus stalks and under tree bark. In this study, our goal was to identify which habitat types beetles were overwintering throughout the agroecosystem, and to characterize five different types of substrates used for overwintering and compare the beetle survival. Ground cover quadrat samples were taken from three habitat types; asparagus fields, weed margins, and woodlots throughout seven commercial asparagus fields in Michigan. The abundance and survival of beetles per quadrat sample was assessed. Additionally, overwintering cages were constructed with five substrates commonly found within and surrounding asparagus fields. Ten adult asparagus beetles were placed into each cage and allowed to overwinter under natural conditions. The highest overwintering abundance, survival, and mortality was within asparagus fields, while the highest survival in cages was in deciduous leaves and lowest in thin bark. Results of this study help us better understand where beetles are overwintering and what habitat types throughout the agroecosystem contribute to pest pressure in asparagus fields. Implications of this research will allow us to develop sustainable pest management strategies for the asparagus industry.