Predators of the asparagus miner (Diptera: Agromyzidae) and the impact of border habitats on their diversity and abundance

Asparagus miner (AM), Ophiomyia simplex Loew (Diptera: Agromyzidae), is a major pest of asparagus and has been identified as a putative vector for pathogenic Fusarium spp. Presently, the naturally occurring predators of AM are unknown, but field observations suggest that spiders are among the predators that consume these insects as adults. The goal of this research was to identify predators for potential conservation biological control efforts for AM and to measure the impact of border habitats on asparagus pest and predator abundance and diversity. Predatory arthropods were collected using sweep nets from 20 asparagus farms in Oceana County, Michigan over a 8-week post-harvest period in 2014. Sweep net samples were taken at transects 10 m into the border habitat, at the field edge, and 20 m into the field. At each transect, the abundance of AM was monitored weekly with yellow sticky traps. Field borders were categorized based on the type of adjacent habitat: asparagus, forest, non-crop, or other crop. To establish predatory linkages to AM, molecular gut content analysis was conducted on collected predators using COI based primers specific for AM.  We compared the distribution of predators and prey over time, sampling location and border type. Overall, our research identified predators as candidates for conservation biological control of AM and has demonstrated that the type of border habitat can impact biological control.