By Scout Nelson
Corn rootworm is a major pest of corn in the United States, causing around $2 billion in annual losses. Though larval feeding is mostly over by mid-summer, there is still time for farmers to act against adult beetles through active monitoring and management strategies.
Corn rootworm completes one generation per year. In Nebraska, adults emerge from mid-July to mid-August, living for up to six weeks. The timing of their appearance is based on degree-day accumulation, but factors like soil type, planting date, and pest exposure can influence this. Females can lay over 1,000 eggs by August or September, leading to new infestations the next year. Since adult beetles have limited daily movement, field-level scouting is vital.
Effective scouting should start around the R1 growth stage in early to mid-July and continue through August. Methods include checking for root injury, setting sticky traps, and counting beetles on whole plants. A root injury score of 0.25 on the Iowa State University scale signals economic damage.
Sticky traps placed in a specific pattern across the field should be checked weekly. More than two beetles per trap per day suggests the need for changes in pest management for the next crop season. Whole plant counts help identify if beetle pressure is high enough to risk yield loss.
Recent research warns of Bt-resistant rootworms moving into first-year cornfields. This highlights the need to scout all cornfields, regardless of planting history.
Key pest control methods include crop rotation, using Bt corn hybrids carefully, and applying insecticides when necessary. However, overuse of sprays can speed up resistance.
Although larval control time has passed, adult monitoring remains essential. Scouting in July and August helps farmers prepare better for the next season and manage corn rootworm risks smartly.
Photo Credit:gettyimages-chrisboswell
Categories: Nebraska, Crops, Corn