Onion maggot continues to be a severe pest in northern climates. This pest has developed high levels of resistance to nearly all insecticides, making it difficult to manage. Conventional tactics are no longer reliable by themselves and effective management requires additional control strategies for reducing onion maggot impacts. Cyromazine is an insect growth regulator used as a seed treatment to control onion maggot under section 18 registration. Our objectives were to 1) evaluate cyromazine’s impact on biological control agents, 2) determine the potential of refuge habitats to increase carabid communities in Michigan onions, and 3) evaluate the combination of cyromazine and refuge strips in onions as a new system for management of onion maggot. In 2000, we looked at the effect of newly established grassy refuges on carabid beetle populations in a Michigan onion field. The carabid activity-density within two-bed refuge strip treatments was not significantly different from the activity-density within two-bed onion control strips. Pterostichus melanarius was the only species more abundant in the newly established refuges than in the onion control habitats. However, the presence of a grassy refuge increased beetle populations in the four-bed crop habitat including entomophagous predators like Poecilus chalcites and Bembidion quadrimaculatum . In 2001 we examined the relationship between refuge habitats established in 2000 and insecticide treatments and quantified their impacts on carabid beetle and onion maggot populations. Conservation practices including the use of narrow-spectrum insecticides and refuge strip habitats will help to optimize the role of generalist predators in the control of onion maggot.
Species 1: Diptera Anthomyiidae Delia antiqua (onion maggot)
Keywords: conservation biological control, refuge habitats
The ESA 2001 Annual Meeting - 2001: An Entomological Odyssey of ESA