Potential Soybean Pests for 2021

A soybean disease that is causing more concern in Nebraska is Frogeye Leaf Spot. It is showing up more in southeast Nebraska and there is concern that it may be resistant to the Qol (Group 11) fungicide which includes Stobilirins. Quadris is a popular fungicide that Frogeye Leaf Spot has been found to be resistant to. In Nebraska 10 counties have identified soybeans that have been infected with Frogeye Leaf Spot resistant to fungicides. Research is being conducted if any counties in southeast Nebraska had this resistant fungus in 2020. In 2020 there was also a significant amount of SDS (Sudden Death Syndrome) in southeast Nebraska. If you do have soybeans that have the symptomology of SDS, you may also want to check for SCN (soybean cyst nematode), as many times if you have SDS, SCN will also be present in the soil. These two diseases have a symbiotic relationship, many times coexisting in the soil together. A disease with similar symptomology as SDS is brown stem rot. By closer examination these two diseasescan be identified. If you have not had your fields tested for SCN recently, the Nebraska Soybean Board has a program that will pay for having your soil tested for SCN for free. Check with you local Extension office for sample bags. If you are in the counties of Richardson, Nemaha, Pawnee, Johnson, Otoe or Cass, contact me at glesoing2@unl.edu , (402) 274-4755 or (402) 274-9639 (cell) about sampling for SCN. I have a soil probe, that you can borrow or I can sample some fields as well. Your ag supplier may also provide this soil sampling service. If you have SDS or SCN in your soil what can you do about it? For SDS, there are soybean varieties that have good resistance. There are also seed treatments available, ILEVO and also SALTRO. On-Farm research at UNL showed about a 4 bu/ac yield increase when using ILEVO compared to untreated fields. Saltro as a seed treatment for SDS has not been evaluated as much in the area. If fields have a history of SDS in soybeans, a seed treatment and the use of a resistant variety would be good strategy to consider. Finally there is a new source of resistance, PI89772 for SCN. From this source, two varieties are available, Golden Harvest GH2329X and NKBrand S23-65X.
Another pest that has been around for a few years is the soybean stem borer. This insect appears to be increasing as more fields are becoming infected with this insect, such as Otoe county. Until recent years, the primary areas where the soybean stem borer caused issues were in counties that bordered Kansas. University of Nebraska-Extension has a NebGuide G2082 that addresses this pest. It can be found athttps://extensionpublications.unl.edu/assets/html/g2082/build/g2082.htm  If you do identify stem borer in your soybeans, try to harvest these early as possible, due to lodging of the infected soybean plants. If you have a field that has soybean stem borer or know of a field that has this pest near your field,you may want to consider not planting soybeans in that field for a while. Longer season soybean varieties which mature later also are suggested because they have a longer time to harvest before they lodge compared to short-season varieties that have shownto have more harvest losses due to lodging. Finally if you have a problem with soybean stem borer, you may want to consider planting sunflowers as a trap crop. Evidently the soybean stem borer prefers sunflowers to soybeans.
A pest that generally isn’t an issue in southeast Nebraska is the Japanese Beetle. We are seeing more and more of these beetles in the area each year, but to date they have not caused economic damage to corn or soybeans. For soybeans the economic threshold is 30% defoliation during the POTENTIAL SOYBEAN PESTS FOR 2021vegetative stage or 20% during the reproductive stage. Several insecticides are effective in controlling Japanese beetles. Check the insecticide section of your Weed, Disease and Insect Guide for the best product for soybeans. I do know a few years ago some farmers had heavy infestations of Japanese beetle in Cass county and did treat some fields due to heavy defoliation.If you have questions, feel free to contact me at (402) 274-4755, (402) 274-9639 (cell) or glesoing2@unl.edu.
Gary Lesoing
Extension Educator
Nemaha County
January 2021