By Blake Jackson
As western corn rootworm beetles emerge from the soil, growers should watch for signs such as goosenecked corn and increasing beetle populations in fields.
According to Penn State Extension experts John Tooker and Adriana Murillo-Williams, these indicators can signal a healthy rootworm population and may suggest that some beetles are developing resistance to Bt corn traits designed to control the pest.
Western corn rootworm is considered one of the most destructive corn pests in the United States. Its larvae feed on corn roots, weakening the plant's ability to absorb water and nutrients. Severe feeding damage can cause plants to lodge, reducing yield potential and making harvest more difficult.
Crop rotation remains the most effective management strategy in Pennsylvania and neighboring states. Since rootworm larvae cannot survive on crops such as soybeans, alfalfa, sorghum, or sorghum-sudangrass, rotating away from corn can significantly reduce pest populations.
For operations that grow continuous corn, producers often depend on Bt hybrids with belowground insect protection. However, repeated use of the same Bt traits over multiple seasons can increase the risk of rootworm populations developing resistance.
Reports of resistance have already been documented in parts of the Midwest and have also been observed in Pennsylvania.
Growers noticing heavy beetle activity or goosenecked corn should inspect root systems for feeding injury. Although controlling adult beetles at this stage generally does not reduce next year's population, treatment may be justified if beetles are clipping silks and threatening pollination.
For future management, experts recommend rotating crops whenever possible or selecting hybrids with different rootworm-control traits if continuous corn production is necessary. Other options include using soil-applied insecticides or adjusting planting dates to reduce larval survival.
Farmers who experience unexpected rootworm damage should report the issue to their seed company and contact their local Extension office for guidance.
Diversifying pest management practices is essential to slowing resistance development and protecting corn yields over the long term.
FAQs
- What are the signs of rootworm infestation?
Goosenecked corn, lodged plants, and high beetle populations are common indicators.
- Why is crop rotation effective?
Rootworm larvae cannot survive on crops like soybeans or alfalfa.
- Can Bt corn lose effectiveness?
Yes, repeated use of the same Bt traits can lead to insect resistance.
- Should adult rootworm beetles be sprayed?
Usually no, unless they are damaging corn silks and affecting pollination.
- What should growers do after finding rootworm damage?
Report it to the seed company and consult their local Extension educator for management advice.
Photo Credit: istock-urpspoteko
Categories: Pennsylvania, Crops, Corn