David Moseley and Tristan Watson, LSU AgCenter Scientists

If you find irregular patches of soybean plants that look generally stunted, yellow, or dead, the cause could be nematodes. Generally, nematodes jeopardize the root system of the plant. Therefore, the plants will often have symptoms that mimic other maladies such as drought and nutrient deficiency. It is not uncommon to find nematodes throughout Louisiana. A recent survey (2019-2021) detected Southern root-knot nematodes in 22% of 164 fields. Another damaging species, the reniform nematode, was found in over 58% of the fields. During the early months of the growing season it can be difficult to determine if the problem is from nematodes by examining the roots because few if any root symptoms are likely to have developed by this point. Therefore, a sample should be sent to the LSU AgCenter's Nematode Advisory Service to determine if nematodes are present in the soil. For more information on the Southern Root-knot Nematode, read “Southern Root-Knot Nematode on Soybean” from the Louisiana Crops Newsletter Volume 12, Issue 7 – August 2022. If nematodes are determined to be a problem, please evaluate the performance of varieties tested by the LSU AgCenter such as in the 2023 Soybean Variety Yields and Production Practices.

Figure 1. Irregular patches of poor growing soybean plants that were infected by Southern root-knot nematodes. This picture was taken in Morehouse parish in 2022.

Figure 2. Southern root-Knot infected soybean plants that have poor growth and development symptoms. This picture was taken in Morehouse parish in 2022.