Research articleBiocontrol on the edge: Field margin habitats in asparagus fields influence natural enemy-pest interactions

•Postharvest pests, asparagus miner and asparagus beetle congregate on field edges.•Predators were found in the highest abundance in field margins.•Sixteen Arachnida and 13 Insecta predator families fed on asparagus miner.•Asparagus beetle was fed on by six Arachnida and seven Insecta predator families.•Incidents of predation were highest in fields with forest or crop margins.

We evaluated pest and predator spatial distributions in relation to asparagus field margins, developed molecular gut content analysis methods for two key asparagus pests, and determined trophic links between the two pests and arthropod predators. Our results indicated that the abundance of natural enemies is higher outside asparagus fields than inside, and fields bordered by forests had higher numbers of predators compared to other types of field margins. We screened 3646 field-collected predators from 10 commercial asparagus fields using molecular gut content analysis in 2014 and 2015, and found that 29 arthropod families feed on the two key pests. Significantly more predators positive for the two key pests' DNA were found in field margins in both years than inside the asparagus field. We highlight the potential significance of unmanaged field margins, particularly forested ones, in providing biocontrol services in agricultural fields.