Field Guide     Pest Management     Seedcorn Maggot

Seedcorn Maggot

CROPS IMPACTED: corn, soybeans, beans, cabbage, peas, potatoes

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Family: Anthomyiidae

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About the Seedcorn Maggot

Reproduction and Life Cycle

The seedcorn maggot has several generations annually. During average weather conditions there tends to be 3, with the first generation often causing the greatest amount of damage. They spend the winter in the ground as pupae, and will emerge as adults in swarms. These flies can be found buzzing near or over recently plowed land. The adults will mate after 2 to 3 days and will lay their eggs in soil that is either high in organic matter or among seeds. The eggs are laid in groups and only take 2 to 4 days to hatch. They can do this even in temperatures as low as 50 degrees Fahrenheit. When the larvae hatch, they will be able to thrive and grow as long as the temperature is between 52 and 92 degrees Fahrenheit. The larvae will remain in the soil throughout all of their instars, feeding off of available seeds. It will take 3 weeks for them to fully develop, which is when they will enter the pupal stage. This stage lasts approximately 10 days.

Seedcorn Maggot Identification and Habitat

Identification

The eggs of the seedcorn maggot are small, elongated, and white in colour. When the maggots hatch, they are pale yellow and about 4mm long. They have no legs, and cylindrical in shape and taper at the rear. The larvae have tough skin and 2 very small black hooks that help them eat. During the papal stage, they are brown, shaped like an oval and are similar in size to a wheat grain. The adults look similar to houseflies, but are about half the size. Varying from light to dark gray in colour, these flies have wings that rest over their body when not in flight.

Habitat

The seedcorn maggot can be found throughout the United States and in southern areas of Canada. This maggot mainly feeds on decaying plant matter, plant roots, different vegetable types, as well as corn and soybean crops. They tend to affect crops in the highest proportions during the spring when weather conditions are cold and wet. The maggots have the ability to burrow themselves into the seed, often ending the germination process. They will also attack new seedlings, eating their roots and first true leaves, which has the ability to destroy the plants growing point. If damage is only minimal, there will be visible holes on the leaves; typically there needs to be 5 maggots per plant for the damage to be significant. Due to the fact that seedcorn maggots are attracted to decaying organic matter, fields that have been manured, or were recently plowed pasture or hay fields are at a higher risk for infestation. Damage can be noticed about 7 days after the plants start to emerge from the ground.

Seedcorn Maggot Management and Control Methods

Management

The problem with seedcorn maggots is that once you notice the damage they caused, it is often too late to treat. This is why taking preventative measures is crucial in order to avoid a significant infestation. It is; however, advised to observe the seedcorn maggot’s population throughout the season to understand when the fly-free periods are. In order to discover this, place yellow buckets with soapy water along the outside of your fields in the beginning of April. The buckets should be placed approximately 100 feet apart. Since insects are naturally attracted to the buckets bright colour, the flies will soon get trapped in the water. Every 4 to 6 days dispose of the old water and refill with new soapy water. Keep track of the captured seedcorn maggot adults so that you can determine when their population increases and decreases.

Cultural Control

For preventative measures against the seedcorn maggot, avoid using green or animal manure on the field and do not plow weeds or cover crops during the spring. It is advised to complete plowing during the fall, as the flies are more attracted to organic matter mixed in with soil that is live. This is why conservation tillage has been effective to lower maggot populations; with the organic matter remaining on the soils surface, it is not as attractive to this pest. Additionally, different types of cover crops used can influence their population level. Cover crops that are a legume lead to higher populations in comparison to a grass type. Another recommendation is to handle the seeds with care in order to prevent your seeds coat cracking. If the coat is cracked, it makes it easier for maggots to feed on the inside of the seed. Use planting methods that will encourage quick germination, such as shallow plantings, late planting when weather is wet and cold, and having seedbeds well-prepared. If you plant your seed during the fly-free periods that were determined by the soapy water scouting method, this can also help avoid infestation. There are natural enemies of the seedcorn maggot, such as certain fungi types, and ground beetles.

Chemical Control

Insecticides available for the seedcorn maggot are only for prevention measures such as using seed that has been pretreated with insecticide, or incorporating an insecticide into the soil before planting. It is important to note that before using an insecticide, read all labels for cautions and proper application. Also, insecticides can kill the seedcorn maggot’s natural enemies; therefore, sometimes an insecticide can cause more harm than benefit.

Latin / Alternative Seedcorn Maggot Names

  • - Delia platura

Sources

http://bugguide.net/node/view/739343

http://www.ipm.ucdavis.edu/PMG/r116300311.html<

http://ento.psu.edu/extension/factsheets/seedcorn-maggot