Whether the focal crops are vegetables, field corn, or soybeans, we’re hearing from growers that poor germination has been an issue this season. The cool, wet conditions we’ve had this spring have delayed seedling germination and growth, and this just happens to be the perfect scenario for seed and root maggots to do their worst damage. Although there are several species of seed and root maggots that attack crops in Indiana, the seed corn maggot (Figure 1) is one species that feeds on a variety of crops in different plant families. The larval (maggot) stage of this insect is headless, legless and feeds directly on the seed, destroying it so that it does not germinate, or it germinates into a weak seedling that will not survive. The adult stage of this insect looks like a small house fly, and the female flies are attracted to disturbed soils with decaying organic matter to lay their eggs.
Figure 1. Seedcorn maggot on a corn kernel. (Photo by John Obermeyer.)
Conditions that slow crop germination and growth, extend the period of vulnerability to seed and root maggots because seeds/seedlings are unable to outgrow feeding damage. Fields with a history of seedcorn maggot infestation, fresh organic matter (tilled cover crops, or manure), and cool, wet soils are at higher risk of damage by this insect. Unfortunately, there is no rescue treatment for seedcorn maggot damage; rather, replanting is the only option. However, cultural practices, such as delaying planting until soil temperatures are optimal for rapid seed germination and delaying planting into fields with fresh incorporated organic matter for at least two weeks can help reduce seedcorn maggot injury. For more details and information about other seed and root-feeding maggots please read Seed and Root Maggots, in an earlier edition of the Vegetable Crops Hotline!