Description of the Pest
The seedcorn maggot adult is a slender, light gray fly, about 0.2 inch long; it is less robust appearing than the housefly. The whitish eggs are slightly curved with their posterior bluntly rounded. Mature larvae range from 0.2 to 0.25 inch in length, are white to whitish yellow, cylindrical, and taper anteriorly. Pupae are small brown capsules. In California, the seedcorn maggot is abundant primarily in spring, during or following a wet cycle, and is most common in fields containing a high amount of residue from a previous crop or where manure has been spread.
Damage
Seedcorn maggots burrow into corn seeds and prevent germination. Slow emergence and poor stand establishment are signs of seedcorn maggot activity. Where slow, spotty emergence is observed, dig up seeds and inspect for maggot feeding. Soil and weather conditions such as cool soil temperature and periods of excessive moisture favoring slow seed germination and seedling emergence increase susceptibility to seedcorn maggot infestation.
Management
A preventive treatment (seed or broadcast) is the best method of control. To reduce attractiveness of a field to egg-laying adults, disc or plow early in the season, incorporating residues from a previous crop and destroying weed growth. Plant under ideal soil and weather conditions to assure rapid seed germination and minimize the seedcorn maggot problem.
Organically Acceptable Methods
Discing to incorporate crop residues and destroy weed growth and planting under ideal conditions are the best way to manage this pest in an organically certified crop.
Pesticides and Natural Enemy Releases
Not all registered pesticides are listed. The following are ranked by their IPM value, with the most effective and least harmful to natural enemies, honey bees, and the environment listed at the top of the table. When choosing a pesticide, consider information related to water and air quality, resistance management, and the pesticide's properties and application timing. Use PestManage to compare summarized management options for different pests in the same crop. Always carefully read the label of the product being used and take all necessary precautions when handling pesticides.
| Rank | Active ingredient | Example trade name | Group | Group Order | MoA 1 | Amount per acre | REI (hours) ‡ | PHI (days) ‡ | Comments | Selectivity 2 | Bees 3 | Predatory mites 4 | Predators 5 | Parasitoids 5 | Residue duration 6 | Leaching(fish) 7 | Adsorbed runoff(fish) 8 | Solution runoff(human) 9 | Leaching(human) 10 | Solution runoff(human) 11 | Last updated 12 |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
|
|
Poncho 600 | Preplant | 1 |
4A |
— | 0 | NA | A seed treatment. Do not apply other neo... | narrow | — | — | — | — | — | — | — | — | — | 08/2008 | ||
|
|
Cruiser 5FS | Preplant | 1 |
4A |
— | 12 | NA | A seed treatment. Use allowed under a su... | narrow | — | — | — | none to short | very low | very low | low | high | high | 08/2008 |
Legend
- ‡ a b Restricted entry interval (REI) is the number of hours (unless otherwise noted) from treatment until the treated area can be safely entered without personal protective equipment. Preharvest interval (PHI) is the number of days from treatment to harvest. In some cases, the REI exceeds the PHI. The longer of the two intervals is the minimum time that must elapse before harvest.
- 1 ↩ Group numbers for insecticides and miticides are assigned by the Insecticide Resistance Action Committee (IRAC). Insecticides with unknown modes of action are assigned mode-of-action group numbers (MoAs) that begin with UN. Rotate pesticides with a different mode-of-action group number, and do not use products with the same mode-of-action group number more than twice per season to help prevent the development of resistance. For example, the organophosphates have a group number of 1B; insecticides with a 1B group number should be alternated with insecticides that have a group number other than 1B.
- 2 ↩ Range of insect and mite groups affected by a pesticide. Broad means the pesticide affects most groups of insects and mites; narrow means the pesticide affects only a few specific groups.
- 3 ↩ Risk of harm to honey bees. For more information, see Bee Precaution Pesticide Ratings.
- 4 ↩ Risk of harm to predatory mites. Toxicities are generally to western predatory mite, Galendromus occidentalis. Where differences have been measured in toxicity of the pesticide-resistant strain versus the native strain, these are listed as pesticide-resistant strain or native strain.
- 5 a b Risk of harm to parasitoids and general predators. Toxicities are averages of reported effects and should be used only as a general guide. Actual toxicity of a specific insecticide depends on factors including the application rate, environmental conditions, and the life stage and species of a parasitoid or predator.
- 6 ↩ Length of time residue affects natural enemies. Short means hours to days; moderate means days to 2 weeks; and long means many weeks or months.
- 7 ↩ Risk of harm to fish from leaching, based on USDA Natural Resources Conservation Service Windows Pesticide Screening Tool (WIN-PST).
- 8 ↩ Risk of harm to fish from adsorbed runoff, based on USDA Natural Resources Conservation Service Windows Pesticide Screening Tool (WIN-PST).
- 9 ↩ Risk of harm to fish from solution runoff, based on USDA Natural Resources Conservation Service Windows Pesticide Screening Tool (WIN-PST).
- 10 ↩ Risk of harm to humans from leaching, based on USDA Natural Resources Conservation Service Windows Pesticide Screening Tool (WIN-PST).
- 11 ↩ Risk of harm to humans from solution runoff, based on USDA Natural Resources Conservation Service Windows Pesticide Screening Tool (WIN-PST).
- 12 ↩ Date information was last updated in the UC IPM Pest Management Guidelines.
UC IPM Pest Management Guidelines: Corn
UC ANR Publication 3443
L.D. Godfrey, Entomology, UC Davis
S.D. Wright (emeritus), UC Cooperative Extension Tulare and Kings counties
C.G. Summers (emeritus), Entomology, UC Davis and Kearney Agricultural Research and Extension Center, Parlier
C.A. Frate (emeritus), UC Cooperative Extension Tulare County
Acknowledgement for Contributions to Invertebrates
M.J. Jimenez (emeritus), UC Cooperative Extension Tulare County
