Editor’s note: This article is from the archives of the MSU Crop Advisory Team Alerts. Check the label of any pesticide referenced to ensure your use is included.
Degree-day accumulations (see table in this issue) are favorable for emergence of adults of the early-season maggots (seed corn maggot, onion maggot, cabbage maggot). These species overwinter as pupae in the soil and start to develop when soil temperatures near 40ºF.
Seed corn maggot flies lay eggs near germinating seeds of a variety of crops, including cucurbits, snap beans and sweet corn. They are attracted to decaying organic matter so muck soil and fields with manure or freshly plowed green manure are especially vulnerable to infestation.
Onion maggot flies, as their name implies, lay eggs at the base of onion plants. They are especially attracted to damaged onions. After hatching, the maggots feed on the roots, stem, and developing bulb. Cabbage maggot flies lay eggs on crops in the mustard family (cabbage, broccoli, cauliflower, radish, etc.). After hatching, cabbage maggots feed on the roots of these plants.
Damage by these maggots causes wilted plants (because of feeding on roots) and plant death resulting in reduced stand. Growers planting vulnerable crops when adult maggot flies are laying eggs should protect their crops with a soil insecticide or seed treatment. See MSUE bulletin E312, 2008 Insect, Disease and Nematode Control for Commercial Vegetables, for insecticides registered for control of these pests on various crops.