Many livestock operations did not have much opportunity to spread manure this winter and into the spring. Thus many may have pits and lagoons near full capacity and a great need to move that manure to fields as soon as possible. As spring progresses, manure spreading and planting may occur in a short sequence that can set up prime conditions for seedcorn maggot infestations and injury resulting in poor stand establishment. Factors that favor seedcorn maggot damage include the incorporation of either green material, such as cover crops or weeds, and/or manure, and cool and damp soil conditions that delay seedling emergence. The decaying green material and manure release odors that attract the adult flies. The adult female flies lay their eggs in the soil near the source of the odors of decay. When the eggs hatch, the maggots move to and feed on the decaying organic matter. If crop seeds are germinating in close proximity to the decaying matter, the maggots can move to the seed and begin feeding on the seed and seedling of corn or soybean. There is no rescue treatment only preventative treatments of either seed or soil applied insecticides.
To determine if the stand loss/poor stand establishment is due to seedcorn maggot, one needs to inspect the seed rows. Dig with a trowel or soil knife in the gaps of the row to look for damaged seeds and/or seedlings, and small, white fly maggots or pupae (these resemble brown rice grains). If damaged seedlings are present, inspect the seed stalk for maggots.
Commercially applied seed treatments such as Cruiser 5FS (thiamethoxam), Poncho 600 (clothianidin), and Poncho Votivo (clothianidin) which contain insecticides effective against several soil infesting insects are effective against seedcorn maggot as well. If the seed has not been treated with one of these seed treatments, then a soil applied insecticide such as Capture LFR (bifenthrin) can be used if the planter is setup with application equipment.
As the season progresses, seedcorn maggot becomes less of a concern as soil temperature increases, dampness decreases and seeds germinate and emerge rapidly. Also, the greater the time gap between when green material and/or manure is incorporated into the soil and when seed is planted into the same soil, the less of a risk there is for seedcorn maggot being present.