It's that wonderful time of the year again: fall! As you embellish your homes with pumpkins and various seasonal decorations, it's also the perfect time to consider inspecting your fields for soybean cyst nematodes (SCN). SCN first emerged in Nebraska in 1986 and has since been detected in 59 counties across the state, including all counties in Southeast Nebraska.
While SCN symptoms are not always easily visible in the field and can sometimes go unnoticed, they can result in up to a 30% yield loss. When symptoms are present, you may observe circular patches of yellowed plants in the field, and in severe cases, stunted plants and reduced yields. Research conducted at Iowa State University has demonstrated a high SCN population in fields with hot and dry conditions. So, be extra cautious with this disease this year.
To check if your soybean crop is infested with SCN, you can simply pull up the roots and look for adult female SCN. Initially, they appear pearl-white and lemon-shaped but become brown and more challenging to spot as they mature. Nitrogen-fixing nodules are also present on the roots but are irregular in shape and larger than the cyst nematode. SCN populations are typically highest in the fall after soybeans are harvested. The most effective way to determine whether your field is infested with cyst nematodes is by sampling your soil. For efficient sampling, focus on areas where the yield monitor has indicated low yields, as well as field entryways, field borders, or regions with disease patches. Use a 1-inch diameter soil probe or a spade to collect a minimum of 15-20 soil cores from randomly selected areas at a depth of approximately 6-8 inches. This process should cover an area of about 10-20 acres. Combine the soil from each 10-20 acre section in a bucket and thoroughly mix it. After mixing, place about 2 cups of soil into a soil sampling bag or a zip-lock bag. If you are interested in sampling your fields, UNL Extension in Nemaha County provides instructions on SCN sampling, offers a soil probe for your use, and provides sample bags. It's worth noting that the Nebraska Soybean Board is currently sponsoring cost-free soil testing for soybean cyst nematodes. If you're in the southeast Nebraska area, I'm also available to assist with field sampling.
If you discover SCN in your field, you can manage them by planting soybean varieties that are resistant to SCN. Another effective management practice involves implementing crop rotation with non-host plants such as corn, wheat, or alfalfa. Additionally, there are several nematode-protectant seed treatments available, but it's important to use them in combination with a resistant soybean variety.
For any assistance with nematode sampling or questions about soybean cyst nematodes, you can contact me at (402) 274-4755 or via email at rlamichhane3@unl.edu.
Ritika Lamichhane
Extension Educator
Nemaha County
October 2023