March 2004Diagnosis: Seedcorn Maggot Feeding Damage Description and Biology of Seedcorn Maggots This grower first started noticing the onion starts she had set out 2-3 weeks ago were wilted and stunted. An examination of the rootballs revealed that they were infested with seedcorn maggots. Seedcorn maggots are the larval stage of a fly that infests the seeds and roots of many different vegetable crops. A few days later the problem was detected in the adjacent broccoli bed. Both the onion and the broccoli had been planted in beds that were previously planted in crimson clover. The clover was incorporated only one week prior to planting, and the large amount of undecomposed organic matter in the beds contributed to the maggot infestation because they prefer high organic matter. Control measures: The maggots like moisture, so try not to give more water than the plants need. Crop rotation and sanitation is extremely important and you never want to leave onion culls in the field, because they can harbor larvae that later mature and reinfest fields. Planting as late as possible in the spring allows for rapid seedling establishment (but of course may conflict with market demands). Avoid planting in soils that are high in undecomposed organic matter. If you amend your soil with manure then you want to leave plenty of time for it to decompose before planting. Post-harvest plowing to bury and rapidly decompose crop residues will help to reduce overwintering populations. Row covers or screens placed over transplants can reduce egg-laying activity. This grower decided to replant in a new part of the field and cover the beds with row covers. Diatomaceous earth can be sprinkled over the beds to inhibit fly activity. She will allow 2-4 weeks for cover crops to decompose before planting.Place your mouse over each photo to read the caption.     This page last updated January 8, 2011. |