How to Manage Pests

UC Pest Management Guidelines


Seedcorn Maggot

Scientific Name: Delia platura

(Reviewed 5/13, updated 9/15, corrected 1/17)

In this Guideline:

Description of the Pest

The adult is a light gray fly about 0.2 inch (5 mm) long. Larvae are white, cylindrical, tapered anteriorly, and are also about 0.2 inch (5 mm) long. Larvae can be found inside damaged seeds or in the soil nearby.


Damage generally occurs in localized areas of the field and appears as areas where seedlings have not emerged. Seedcorn maggots hollow out seeds or eat portions of seedlings. Damage is most common in early plantings when the soil is cool, especially in fields with lots of organic matter. Damage tends to be worse on sandier soils.


If cotton follows corn in a crop rotation, seedcorn maggot may become a problem, especially if crop residue is present in soil for the maggot to overwinter on. Once damage occurs it is too late to treat. A slurry seed treatment is the best preventive control if cotton must be planted early in fields with high levels of decaying organic matter. Planting later in spring when the soil isn't excessively moist and soil temperatures are warmer will help to reduce damage by this pest. Also, destroying vegetation from the previous crop at least 1 month before planting should help minimize damage.

Common name Amount per 100 lb seed** REI‡ PHI‡
(Example trade name)   (hours) (days)

Calculate impact of pesticide on air quality
Bee precaution pesticide ratings
The following are ranked with the pesticides having the greatest IPM value listed first—the most effective and least harmful to natural enemies, honey bees, and the environment are at the top of the table. When choosing a pesticide, also consider information relating to air and water quality, resistance management, and the pesticide's properties and application timing. Not all registered pesticides are listed. Always read the label of the product being used.
  (Lorsban 30 Flowable) 5.5 oz 0 0
  PERSISTENCE: Pest: Moderate NE:2 Short
  COMMENTS: Slurry treatment with appropriate delinted seed fungicide. Toxic to fish, birds and other wildlife. Keep out of any body of water and off of the soil surface. Certain formulations emit high amounts of volatile organic compounds (VOCs); use low-VOC formulations (PDF). Regulations affect use for the San Joaquin Valley from May 1 to October 31, 2015 and 2016. Review the Department of Pesticide Regulation's updated fact sheet (PDF).
** Mix with sufficient water to create a slurry.
Restricted entry interval (REI) is the number of hours (unless otherwise noted) from treatment until the treated area can be safely entered without protective clothing. Preharvest interval (PHI) is the number of days from treatment to harvest. In some cases the REI exceeds the PHI. The longer of two intervals is the minimum time that must elapse before harvest.
1 Rotate chemicals 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; chemicals with a 1B Group number should be alternated with chemicals that have a Group number other than 1B. Mode of action Group numbers are assigned by IRAC (Insecticide Resistance Action Committee). For additional information, see their Web site at
2 NE = natural enemies



[UC Peer Reviewed]

UC IPM Pest Management Guidelines: Cotton
UC ANR Publication 3444

Insects and Mites

  • L. D. Godfrey, Entomology, UC Davis
  • P. B. Goodell, UC IPM Program and Kearney Agricultural Research and Extension Center, Parlier
  • E. T. Natwick, UC Cooperative Extension - Desert Research and Extension Center, Imperial County
  • D.R. Haviland, UC Cooperative Extension, Kern County and UC IPM Program
  • V. M. Barlow, UC Cooperative Extension, Riverside County and UC IPM Program
Acknowledgment for contributions to Insects and Mites:
  • E. E. Grafton-Cardwell, Kearney Agricultural Research and Extension Center, Parlier
  • N. C. Toscano, Entomology, UC Riverside

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