The Japanese beetles are invading corn and soybean fields in the Midwest. Mild winters and earlier-than-normal planting conditions (first 2 weeks of April) will create a suitable environment for emerging beetles to wreak havoc on pollinating corn fields. I have noticed increasing pressure from these beetles in the eastern part of Kansas. Some farmers have sprayed for these insects in pollinating corn fields and in parts of Missouri high numbers of Japanese beetles have been noticed in corn and soybean fields. Japanese beetles can injure corn fields during multiple stages in the insect’s lifecycle. In the spring, overwintering grubs can feed on root hairs decreasing a plants ability to find nutrients and moisture and the adult beetle can defoliate the corn plant to levels warranting treatment. Economic damage most commonly occurs to corn fields because the beetles will congregate on the ears and feed on the emerging silks which can significantly reduce pollination and yields. Typically where you find one on an ear, you will find many because they release a pheromone which attracts other beetles to that feeding site. It is important when scouting to look beyond field edges which typically will have higher numbers of feeding Japanese beetles, and look throughout the field as feeding could be much less. Economic thresholds can be met when silks are clipped to less than ½” before 50% of the field is pollinated, and/or 3 or more Japanese beetles per ear. Defoliation estimates need to be made when determining economic thresholds for soybeans. Typically Japanese beetle feeding alone does not warrant treatment but multiple pest feeding together will. Defoliation is much more of a problem when soybeans are flowering and pod fill is taking place - 20% defoliation at this time call for chemical treatment.
- Be prepared for grasshoppers, scout grassy field margins and if 20 to 30 grasshopper nymphs are found per square yard than treatment is warranted (10 to 15 in the field)
- The recent blessing of rains efforts need to be made in scouting fields for Grey Leaf Spot (GLS) especially on low lying fields along creek and river bottoms, and where irrigation is present. Conditions are right in river valleys, north central Kansas, and around the Dodge City area.
- If you missed an opportunity to double crop, or if you had a crop failure consider trying a cover crop mix to improve soil health, add N, reduce weed pressure, and/or to conserve moisture for next years crops.
If you have any questions, contact your local Hoegemeyer District Sales Manager or Agronomist.