Field Crop Insects - Joanne Whalen, Extension IPM Specialist. True armyworms and cutworms continue to be found in both conventional and no-till fields. Low levels of European corn borer larvae can now be found in the earliest planted corn fields. The best time to control corn borers is before larvae move deep into the whorls or at the pre-tassel stage when larvae are exposed to the spray. The most common leaf feeding damage found in early planted soybeans is from the bean leaf beetle.
Damage appears as small circular holes in the leaves.
No controls should be needed unless you find 2 beetles per foot of row and the stand is being reduced. A pyrethroid or Sevin will provide control. Grasshopper activity continues to increase, especially in no-till situations. Early control of nymphs will generally result in the most effective control. Treating non-crop areas may also help to prevent whole field treatments at a later date.