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May 2000 |
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Seed-corn Maggots Attack Soybeans and Other Insect Problems |
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Seed-corn Maggots & Other Insect Problems Jim Jarman
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Seed-corn maggots, fly larvae that, as the name implies, attack seed corn, are eating newly planted soybean seeds this year. Actually, seed-corn maggots attack numerous field and garden crop seeds. Corn seed are just the most commonly found seed damage by seed-corn maggots. Wayne Bailey, University of Missouri Associate Professor of Entomology, toured bean fields from Mexico, Mo., to Paris, Mo., last week and commented that he had never seen that much damage from this pest before. Some farmers are already replanting fields where stands have been reduced by 75 percent or more. In the past small pockets of infestation have been seen but not whole 40-acre fields. When the beans fail to come up, farmers digging up the seed are finding three and four maggots per seed. The maggots, immature flies, look like regular house fly larvae. The adult fly looks like a small, skinny housefly. Generally, they stay close to the ground, but may congregate on people. During years past, the maggots have been a bigger problem on newly planted corn. But, now hybrid seed corn comes treated with insecticide for control. Since the maggots have not been a major soybean pest in the past the seed is not currently treated. Soybean seed going into replanted fields should be treated. Both Sorghum Guard and Kernel Guard Supreme insecticides are labeled for seed-corn maggot control on soybeans. All of the damage seen so far has been in tilled fields. This appears to be another plus for no-till plantings. The flies are attracted to rotting organic matter. Tillage must start decomposition of the crop residue, which attracts the flies. Bailey discussed the new pest problem with University of Missouri Extension regional agronomists taking part in a weekly teleconference from the MU College of Agriculture, Food and Natural Resources in Columbia. Specialists report a wide range of insects attacking corn and beans. Wireworms and cutworms are eating corn. Soybeans have bean leaf beetles are chewing holes in the leaves and spider mites are causing leaf yellowing in the new crop. Chinch bugs are beginning to move from maturing wheat fields into nearby cornfields. Dr. Bailey urged farmers to regularly scout their crops to find emerging problems. The source for this article is Wayne Bailey (573) 882-3828 baileyw@missouri.edu. We have not had as serious cutworm problems in Callaway County as in other central Missouri counties. Audrain County has had several fields treated for this pest. The corn has grown large enough in most fields to be resistant to cutworm and flea beetle damage. The field crop scouts are beginning to search for European corn borer egg masses in the older, taller corn. The weekend rains have probably helped in controlling or suppressing several crop and garden pests like potato leaf hoppers, spider mites, chinch bugs, thrips, and smaller caterpillars. Moist, humid conditions will promote fungal diseases that are hard on many insects. Unfortunately, the moisture may allow grasshoppers to emerge well from the soft soil.
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