(Posted Wed. Aug 21st, 2013)

Aug. 21: While much of the Midwest experienced a cool, wet spring, farmers should still remain vigilant in monitoring for corn rootworm pressure. Last summer, the stress of the drought may have intensified stress on the corn crop and resulted in small root masses and heavy corn rootworm pressure, but the possibility of corn rootworm remains even under the less conducive circumstances of 2013.


Since adult corn rootworm beetles prefer to feed on pollen and fresh corn silks, late planted corn can act as a trap crop for adult corn rootworm beetles. The increase in beetles may lead to increased silk clipping, interfering with pollination and leading to a high number of egg-laying females. Diligent scouting remains the farmer’s best defense against this threat.


Farmers should consider scouting sooner rather than later as August marks the peak of adult corn rootworm beetle activity. Given the planting delays experienced this spring, continuing scouting into September is advisable as beetle activity may also peek later in 2013.


Scouting plays an integral role in insect management. Thus, employing regular, appropriate scouting techniques is essential.


Fields should be scouted for corn rootworm beetles regularly and sampled weekly. Additionally, proper scouting techniques include:


  • Randomly selecting 10 to 25 locations within the field and counting the total number of beetles on at least two plants within each location. The minimum number of plants sampled should be 20 to 50 depending on the field size and activity level of beetles.
  • In between beetle counts, collect beetles to determine the number of males and females in a sample. Corn rootworm beetles can be captured by hand, with a small sweep net or use of a motorized hand-held vacuum.


Scouting provides valuable information about insect and disease pressure in this year’s crop and help decision for next year’s seed choice. In-season scouting, using the correct corn trait package and following an appropriate crop rotation strategy can be extremely effective in controlling corn rootworm, protecting personal investment in the crop and optimizing yield.