By Blake Jackson
As silage harvest gets underway, Pennsylvania corn growers should pay close attention to signs of western corn rootworm, particularly in fields where corn has been grown continuously.
According to Penn State Extension entomologist John Tooker, this pest is generally less concerning in fields rotated with soybeans or other crops because crop rotation can interrupt its life cycle. Continuous corn, however, can create favorable conditions for rootworm populations to build over time.
During harvest, growers should watch for corn plants that are lodged or show pronounced goosenecking. Although adult rootworm beetles typically emerge from the soil in late July and early August, damaged or leaning plants can provide clues that significant rootworm activity occurred earlier in the season.
When lodging is present, digging up affected plants and examining their root systems can help determine whether root feeding contributed to the damage. Even when roots have produced new growth after plants began leaning, earlier feeding injury may still be visible.
Rootworm damage can also occur in fields planted with newer transgenic hybrids designed to provide protection against the pest. A recent observation in a Centre County continuous-corn field illustrates the concern.
Numerous plants had lodged despite being planted with a hybrid believed to contain multiple rootworm-targeting traits, including a newer technology. Further investigation is needed, but the situation highlights an important issue: western corn rootworm populations can develop resistance to available transgenic traits.
Growers and agronomists should evaluate rootworm control performance this season and use those observations when developing management strategies for 2027.
Monitoring fields now can help identify potential problems early and support better decisions about crop rotation, hybrid selection, and other control measures.
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Categories: Pennsylvania, Crops, Corn