How Insect Pests Affect Crop Quality in Corn and Soybeans
While early season insect control is a key to achieving yield potential, late-summer insect pests threaten crop quality. Feeding damage creates opportunities for fungal infection or rot and may trigger dockage at the elevator. Key insect pests include corn rootworm beetle, Japanese beetle, Mexican bean beetle and grasshoppers. Late-season lepidopteran worms such as corn earworms, western bean cutworm and European corn borer can damage ears and pods.
Watch for Larval Injury
If adult corn rootworm beetles are swarming in corn, this could be a sign that significant rootworm larvae numbers have survived the hybrid’s rootworm trait protection. Look for lodged plants and dig up some corn roots to inspect for feeding. Wash roots in a bucket of water, then look for brown lesions on injured root tips and nodes. Pruned roots are less capable of supplying water and nutrients to growing ears; moderate to severe root pruning may result in lodging and significant losses at harvest. Growers have had success controlling corn rootworm beetles with DuPont™
Lannate® LV insecticide.
Larval injury may make roots more susceptible to root and stalk rot fungi, even on hybrids with rootworm-resistant traits. Corn-on-corn growers in particular may need to rotate crops or consider insecticide control of adult beetles. One western corn rootworm beetle female typically lays 800 eggs in the soil to wait for next season’s corn crop. An average of one beetle per plant is considered an economic treatment threshold.
Pests Hurt Yield
Western bean cutworm can also threaten corn yield and quality. Moths tend to lay eggs in early July. Larvae hatch, feed on silks, then burrow into ear tips where they grow quickly and cause significant yield and quality problems. DuPont Pioneer hybrids with the Herculex I (HX1) and Herculex XTRA (HXX) traits provide in-plant protection against Western bean cutworm. Hybrids without an effective trait may require protection from an insecticide with residual control and the ability to be absorbed systemically into the plant.
Soybean aphids may not be a problem now, but could quickly become an issue if dry weather allows populations to grow. The treatment threshold for soybean aphids is 250 aphids per plant.
The information provided on this website is for reference only. Always refer to the product labels for complete details and directions for use.
*In line with Integrated Pest Management and Good Agricultural Practices, insecticide applications should be made when pollinators are not foraging to avoid unnecessary exposure.