Seedcorn Maggot

A fly that lays eggs in the soil near the base of plants, the hatched maggots eat plant roots, seeds, and stems.

   Adults are a dark gray fly looking similar to a house fly but are about ½ their size, they seem to be attracted to the moisture around newly planted seeds. adults overwinter in pupal cocoons in the soil and emerge in the spring and early summer, damage seems to be greater in wet cool years. After mating they lay 75 to 200 whitish yellow elongated eggs near and on stems, and in cracks in the soil, having  3 to 5 generations per year.    Eggs hatch within a few days and reach adulthood in 3 to 4 weeks, the tiny maggots burrow into the soil eating seeds roots and stems, damaged seeds may germinate but leave you with a weak plant without enough energy to grow.The holes and tunnels they make can allow rot to set in. Maggots grow to ¼ to a ⅓  inch long are whitish yellow, legless with tapered or pointed heads. As temperature and humidity rise during the summer, seed corn maggot adults are often attacked by fungal pathogens. The infected flies are found dead and in large numbers clinging to crops, weeds, etc.

In greenhouses, heat the area and keep the soil at 65F for 21 days before planting this will disrupt the feeding pattern leaving them nothing to feed on and to reproduce another generation.

Use Diatomaceous Earth in and on soil to kill maggots and reduce egg laying

Place a collar  around the plants, pressed a few inches deep into the soil

Use Beneficial Nematodes (Steinernema feltiae) they can kill over 230 soil pests

Also try

Reducing  rotting organic matter

Reduce the use of manures

Use sticky traps to catch adults

Use row covers

Chemical control

Follow directions and your state and local laws when using insecticides, you may want to contact your local cooperative extension office to obtain a private applicator’s pesticide license they will teach you the proper application of chemicals and how to handle them safely.

Systemic insecticides will kill the chewing maggots but young plants and seeds cannot survive the damage they incur before the maggots die, a pyrethrin drench may be effective. Imidacloprid insecticides work very well, you can treat the soil in your patch and also the seed starting mix before transplanting. If you see flies in a covered hut or greenhouse they are probably the fly stage , the interior plastic of a hut can be sprayed with a Bifenthrin insecticide