Hairy Black Fly

What plants are at risk?


Seedcorn maggots attack a wide range of horticultural crops including beans, peas, cucumber, melon, onion, corn, pepper, potato, soybeans and other vegetables.


How do they damage the seeds?


Seedcorn maggots damage newly planted seeds by feeding on seed contents. Often, the shells of the seeds are empty and germination is greatly reduced. Seedlings that do emerge are spindly with few leaves. Damaged seed may germinate, but there are not enough food reserves left in the seed for the plant to survive. Maggots also attack the underground stems of sprouted seeds, resulting in weakened seedlings that seldom survive. 


What does it look like?


Adult - Gray, black-legged fly has scattered bristles on its body and is approximately 5 mm long. 


Egg - Each white, elongate egg has a rough surface and is about 1 mm in length. 


Larva - The maggot is yellowish, white and about 1/4 inch when mature. The body is legless with a pointed head and a blunt tail.


Pupa - The last larval skin hardens to form a puparium (about 5 mm long) in which the pupa develops. The ivory puparium gradually turns reddish-brown as the pupa matures.


Life Cycle:


The adult flies emerges late April and early May. Eggs are deposited on or near the soil surface. Eggs hatch in a few days and the maggots work their way into the soil in search of food. The seedcorn maggot survives the winter in the pupal stage.


The time required to grow from egg to adult is between 3 to 4 weeks. There are 3 to 5 generations each year in Pennsylvania.


What to do if I have Seedcorn Maggots?


Seeds planted early, when the weather is cool and wet for long periods of time are potentially at greater risk to damaging infestations. Planting in well prepared seedbeds is can prevent injury. Shallow planting will increase germination rates, aid in speeding up germination and reduce losses to Seedcorn Maggots. Under these conditions, higher seeding rates should be considered to offset stand loss. Use Eight Flower & Vegetable Granules. After damage is observed on the crops, rescue treatments are not usually effective. Resetting or replanting of crops may be necessary if stand loss is severe.