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Special Edition   April 20, 2009

INSECT PROBLEMS IN WET SOILS ARE PROBLEMATIC

Although the focus is on the recovering from the floods and getting ready for spring planting right now, the wet soils can impact the potential for insect problems. Floods change the natural balance of insect populations and produce conditions that favor those insects adapted to wet soils. Seed corn maggots (see photograph), springtails, cutworms, wireworms, white grubs are some examples of insect pests that will likely be common in wet soil conditions. These subterranean insect pests can cause significant stand loss in crops. The severity of the insect damage will depend on which crop and insect, and planting date. For example, late planting reduces the risk of wireworm damage which is more problematic early in the season. Or, late-planted soybeans are at reduced risk of injury caused by bean leaf beetle, because beetles wait for the first emerging soybean field to lay eggs. In some areas, it will be a long wait and many bean leaf beetles will perish without laying eggs. Nonetheless, producers may be required to use supplemental control strategies for insect pests during wet years.

Seed corn maggot
Seed corn maggot

There are a number of broad spectrum insecticides that have been approved for control of these insect pests. Refer to the most recent NDSU Extension Service "Field Crop Insect Management Guide" (http://www.ag.ndsu.edu/pubs/plantsci/pests/e1143w1.htm) for a listing of currently approved insecticides. Banding insecticide is easier to do with corn planting equipment than with a drill when planting soybeans or small grains. Commercially applied seed treatments, such as Gaucho, Cruiser or Poncho are effective in controlling wireworms and seed corn maggots but provide only suppression of white grubs and cutworms. The high rate of seed treatments should be used and requested at the time ordering seed.

Janet Knodel
Extension Entomologist
janet.knodel@ndsu.edu


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