Crop Rotation Remains the Most Effective Defense Against Rootworm
As western corn rootworm beetles begin emerging from the soil, corn growers are encouraged to closely monitor fields for warning signs that could indicate rising pest pressure.
Curved or "goosenecked" corn plants and increasing numbers of adult beetles may signal a strong rootworm population and the possibility that some insects are becoming resistant to Bt corn traits.
Penn State Extension specialists John Tooker and Adriana Murillo-Williams advise producers to stay alert during this period, as western corn rootworm remains one of the most damaging insect pests affecting U.S. corn production.
The larvae feed on corn roots, limiting the plant's ability to absorb water and nutrients. Severe root injury can cause plants to lodge, lower yields, and complicate harvesting.
Experts emphasize that crop rotation continues to be the most reliable strategy for reducing rootworm populations in Pennsylvania and nearby states. Because the larvae cannot survive on crops such as soybeans, alfalfa, sorghum, or sorghum-sudangrass, rotating fields out of corn disrupts the pest's life cycle and helps prevent infestations.
For growers producing continuous corn, Bt hybrids with belowground insect protection remain an important tool. However, relying on the same Bt traits year after year can encourage resistance. Cases of Bt-resistant western corn rootworm have already been confirmed in several Midwestern states and have also been identified in Pennsylvania.
Producers observing high beetle populations or lodged corn should inspect root systems for feeding damage. While insecticide applications against adult beetles generally do not reduce next season's populations, treatment may be warranted if beetles are clipping corn silks and interfering with pollination.
Extension experts recommend diversifying pest management practices by rotating crops, selecting hybrids with different rootworm-control traits, using soil-applied insecticides when appropriate, and adjusting planting dates.
Farmers experiencing unexpected damage should notify their seed company and contact their local Extension office for management recommendations.
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