Sample for nematodes to protect yield potential
The change in cropping systems in Mississippi in recent years has led to increased concerns about nematode infestations of soybeans. The effect of these changes are:
- Increased acreage of corn that may be rotated with soybeans has led to heightened concern about soybeans being infested with RKN.
- Growing soybeans on sites once devoted to cotton has led to heightened concern about soybeans being infested with RN.
Because of cropping system changes, the need to sample for nematodes has become even more important because of the added risk of infestations from RKN and RN as well as SCN.
- Why sample? Properly collected and evaluated soil samples are the best tool for detecting the presence and species of nematodes in the soil.
Properly analyzed samples will indicate where control practices are not needed, and conversely will indicate where control practices are needed to protect yield potential.
- When to sample? Predictive sampling (sampling to determine if nematode problems are likely to affect a future crop) should be done when population densities are high to decrease the risk of not detecting the presence of a damaging species. Thus, the best time to sample is generally near or just after harvest.
- Proper sampling protocol can be found at MSUcares, Virginia Tech Extension, Univ. of Georgia Extension, Univ. of Georgia Dept. of Plant Path.
The following management tenets should be followed depending on test results.
- If test results indicate that the above nematode species are not present in a field, care should be taken to prevent their introduction since nematodes can be moved from field to field by soil that is transported on field equipment.
- If test results indicate the presence of nematodes, the management goal is to keep the nematode population as low as possible since they are very difficult to eliminate. This involves using management practices presented in the above-cited article for each nematode species.
- Crop production practices that provide adequate nutrients and water and minimize stress due to insects, weeds, and diseases will enhance soybeans’ ability to withstand some nematode feeding damage, but will not prevent yield loss where infestations are severe.
Below is the important take-home message from the above discussion.
Sampling for nematodes should be considered as important as sampling for soil fertility. This is especially true if there is no history of nematode sampling on either old or new soybean production sites. Once documentation of the absence or presence of nematodes is established for given fields, then management options outlined for either case in the above-cited article can be adopted.