NDSU Extension - Ramsey County


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May 14, 2012 Agriculture Column


This past weekend I got a lot of grief about using Howdy to start my columns and now I am even convinced more that I will continue using it as it makes me know that people are looking it over.  My son and son-in-law even talked they would start writing an addition to this letter to let you know what is going on “on the farm” section.  We will have to wait and see how that happens, I am guessing not.  I have include info on cutworms today as they have been on the prowl.

Since insects are temperature-dependent for their development, it is not surprising that insects are emerging earlier than normal with the warm winter and early spring. Some insects are already starting to appear in our field crops. So, scouting is essential to look for any early season insect infestations. Here are some insect pests to watch out for and scouting tips.

CUTWORMS, probably Army cutworms or Pale western cutworms, are being observed in row crops, such as canola, in southwest North Dakota. Cutworms belong to the moth family called Noctuidae. Larvae (worms) are dark colors (brown to gray) with various markings, and up to a pencil in width and 1½ inches in length when mature. Minnesota and Nebraska are reporting large numbers of adult cutworm moths at house lights during evenings. These moths will be moving our way with southerly wind flows. Cutworm larvae cause damage by cutting the seedling off at the ground or below the ground. Larvae can be found by digging in the soil around the base of freshly cut plants. When disturbed, larvae curl up into a ball. As damage continues, fields will have areas of bare soil where the crops have disappeared. Row crops are often more susceptible to cutworm damage than small grains, because cut plants do not grow back (grains compensate by tillering). Rescue foliar treatments are warranted when cutworms exceed the following action thresholds by crop:


Spraying timing is the most important aspect of controlling cutworms. Insecticides are ideally targeted at the young larvae, which are easier to kill than the larger larvae (>1 inch). Use the higher labeled rate of an insecticide for longer residual and apply insecticide at night when cutworms are actively feeding. There are questions about tank mixing insecticides with herbicides for early season weed control. When tank mixing early season herbicide burn-down with an insecticide, you will only get partial control, because cutworms will continue to emerge over a three week period and insecticide residual will not last long enough to kill the late-emerging cutworms. Assuming that the field is at action threshold for cutworms, the best insecticide timing is to apply insecticides right at crop emergence, so you get optimal residual and crop protection against cutworms. There also have been some questions about applying an at-plant insecticide, such as in-furrow or T-band application for control of cutworms. An in-furrow insecticide application is generally not as effective in controlling cutworms as a T-band application. Since cutworms crawl on the soil surface, a 5-7 inch T-band application over the seed furrow would provide better cutworm control.

For insecticides registered in North Dakota for cutworm control, consult the 2012 Field Crop Insect Management Guide at:  http://www.ag.ndsu.edu/pubs/plantsci/pests/e1143w1.htm


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