By Michelle Infante-Casella, Agricultural Agent, Rutgers NJAES Cooperative Extension, Gloucester County
Seed corn maggots survive through winter in dark brown capsules underground. Flies emerge out of soil March or April in New Jersey and can have several generations.
One benefit of this spring, in 2013, is conditions have been drier, with less rainfall, than in past cooler spring seasons. Along with cool weather, this pest thrives under wet conditions too. When the weather is dry, eggs and maggots can desicate to the point of mortality.
Seed corn maggots are pests of beans, peas, cucumbers, squash, melons and corn. They rarely affect pumpkin fields since pumpkins are seeded when soil and air temperatures are warmer and the populations of this pest have declined.
In springtime, when soils remain cool, germination of cucurbit and other seeds is slow and plant emergence takes longer than during summer months. Additionally, during cool and wet spring conditions, the seed corn maggot is active looking for sites to lay eggs. They are attracted to areas with organic matter, fields that have had manure applications and where soils have been disturbed (planting beds or planting holes in plastic mulch. Adult flies will lay eggs just beneath the soil or at the base of the plants that are young seedlings. They can affect both seeded and transplanted cucurbits. Eggs hatch quickly and maggots feed on the seed or seedling. From the time of hatching to the time the maggot turns into an egg-laying adult is approximately 3 weeks.
When scouting fields for this pest, small flies that are smaller and longer than a house fly can be seen near the soil surface. Additionally, if you notice wilt of young seedlings check the lower stem to see if it is hollow and if maggots are present. In fields where germination is spotty, dig up seed that hasn't germinated to see if maggots are inside feeding on endosperm.
When planting your first fields of cucurbit crops try to select fields that warm quickly and fields that have good drainage and do not remain wet for long periods. Also, be sure not to place seed too deeply. Deeper plantings mean colder soils that can slow germination and give more time for the maggots to destroy the seed or seedling. If seed corn maggot is a potential concern, delaying planting until soils reach 55 degrees or higher can help prevent damage. Plants will germinate more quickly and grow more quickly, allowing them to ward off this pest.
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The points of contact between Rutgers Cooperative Extension Service and the grower & business communities are the NJ County Agricultural Agents. The agents are a tremendous source of information for both new and experienced growers. Visit your local county extension office.