By Scout Nelson
Corn rootworm adults begin emerging during mid-summer and remain active until the first hard frost. These insects are among the most important corn pests because their larvae damage corn roots while adults feed on silks, leaves, tassels, and developing kernels. Regular monitoring helps farmers identify population levels early and plan effective management strategies for both the current and future growing seasons.
Adam Varenhorst, Associate Professor & SDSU Extension Field Crop Entomologist, together with Philip Rozeboom, Patrick Wagner, and Amanda Bachmann, encourages producers to monitor corn rootworm populations carefully throughout the season. Their guidance highlights that early scouting helps reduce crop losses, improve pest management decisions, and protect future corn production.
Both northern and western corn rootworm adults can be found in corn fields during summer. Northern corn rootworms are green beetles, while western corn rootworms are yellow with black stripes. Monitoring adult populations provides valuable information about possible root damage during future corn crops and helps determine whether additional management will be needed.
Yellow sticky traps are commonly used to monitor adult populations. Several traps should be placed throughout each field and checked every week during July and August. If trap captures average more than two rootworm adults per trap each day for one week, producers should prepare to manage rootworms when corn is planted in that field again.
Farmers should also inspect corn silks because adult beetles often feed on them during pollination. Silk clipping can reduce successful pollination if it occurs before pollination is complete. Fields should be scouted by checking several plants in different locations and measuring silk length. If silks are clipped to less than one-half inch on 25% to 50% of plants before pollination finishes, a foliar insecticide application may be needed.
Adult beetles may also feed on corn leaves, tassels, and developing kernels. During pollen shed, farmers should count beetles on randomly selected plants. If an average of five or more beetles are found per plant, insecticide treatment may be recommended.
Photo Credit: pexels-pixabay
Categories: South Dakota, Crops, Corn