Bean, snap-Seedcorn maggot

Delia platura

Pest description, crop damage and life history


Pest monitoring Slow emergence and poor stand establishment are signs of seedcorn maggot activity. Where slow, spotty emergence is observed, dig up seed and inspect it for maggot feeding. Cool soil temperature and periods of excessive moisture favoring slow seed germination and seedling emergence increase susceptibility to seedcorn maggot infestation. If you are planning to use untreated bean seed in a certified organic planting, sow a handful of seeds several places in the field, water, and flag the sowings one week prior to your field planting date. Inspect the test seeds the day prior to planting the field. If fifty to seventy five percent of the trial seeds are infested with seed corn maggot, consider delaying or abandoning the sowing of untreated seed in the field for this growing season.

Management-cultural control

To reduce attractiveness of the field to egg-laying adults, disc or plow early in the year, incorporating residues from a previous crop and destroying weed growth. Allow a minimum of three to four weeks between disking in manure and planting bean seeds. Plant under ideal soil and weather conditions to assure rapid seed germination and minimize the seedcorn maggot problem.

One of the most reliable control methods now in general use is to plant seeds that have been treated with an appropriate insecticide. Most commercially available bean seed is treated with an insecticide to protect the seed from insect pests during storage. However, do check the label. Remember, seed treatment alone may not be sufficient to provide field protection against seedcorn maggots. A planter box seed treatment insecticide at planting is recommended.

Management-chemical control: HOME USE

  • bifenthrin
  • gamma-cyhalothrin
  • zeta-cypermethrin

Management-chemical control: COMMERCIAL USE

  • phorate (Thimet 20G)-Do not exceed 1.5 lb ai/a. PHI 60 days. REI 48 to 72 hr. At planting time only. Do not graze or feed to livestock. Toxic to fish and wildlife.