Be Aware of Summer Crop Insect Pests

With some crops being replanted in areas where there was hail damage, newly seeded crops are just coming up and susceptible to insect damage. As we move through the summer, older soybeans are also susceptible to insect pests. It is just important to scout fields periodically to monitor new infestations of pests. Also, CropWatch, https://cropwatch.unl.edu/ is a good resource for information on current crop conditions in Nebraska.  In southeast Nebraska, we have been subject to isolated infestations of insect pests over the years. More recently the thistle caterpillar, which is the larval stage of the Painted Lady Butterfly. Many people were concerned about the millions of butterflies that invaded us, but it is larval stage which come from the eggs that the butterflies lay that can cause defoliation of soybeans. There were some fields that required treatment in southeast Nebraska. Another pest that showed up was the garden webworm. These types of insects would cause more issues with newly replanted soybeans due to much less foliage. Generally soybeans in the vegetative stage require treatment when defoliation reaches 30%. Here is a link to a graphic reference showing different levels of defoliating; https://cropwatch.unl.edu/soybean-defoliation-7-24-09 . Defoliation usually is not as much as we think it is, so good to have a reference.

JapaneseBeetleAnother pest that will be showing up soon is the Japanese Beetle. This pest usually doesn’t defoliate soybeans at levels that require treatment, but we haven’t ever had seedling soybeans around when Japanese beetles invaded us in the summer either. Here is a resource from CropWatch; identifying it and providing control measures; https://cropwatch.unl.edu/2019/japanese-beetles .

Another pest that is a major concern to farmers is the soybean gall midge. This has impacted several areas in Otoe, Cass and Lancaster Counties in soybeangallmidgesoutheast Nebraska. It has not been a major issue yet in the most southern counties of southeast Nebraska.  Nebraska Extension is doing considerable research on the soybean gall midge. They have a number of adult traps around to monitor the emergence of the adults. Once the adults emerge they are looking for young soybean plants to lay their eggs. Usually soybeans in the V2 stage of growth have a crack in the stem where the soybean gal midge can lay it’s eggs. The V1 stage doesn’t not have this yet. Soybean gall midge infestations usually start around the edges of fields and work inward. For more info on this pest, go to https://soybeangallmidge.org/.

For farmers that grow alfalfa, I have seen a lot of hay down with some that has just been harvested. The potato leafhopper has been identified in leafhopperGage County earlier in June. These pests can cause significant damage to first-year alfalfa. Check your regrowth on your alfalfa for a yellow or purple triangle on the leaf tip. Here is a CropWatch resource on the potato leafhopper and treatment guidelines; https://cropwatch.unl.edu/start-scouting-potato-leafhoppers-alfalfa-unl-cropwatch-july-3-2013 .

If you have other questions about any of these pests, contact me at glesoing2@unl.edu or (402) 274-4755 or (402) 274-9639 (cell).

Gary Lesoing
Extension Educator
Nemaha County
June 2022