Managing nematodes begins with knowing the nematode species and population present in the field. This information can be determined by thoroughly sampling each field close to harvest and sending the samples to a nematology laboratory for analysis.1
The accuracy of information increases with the number of samples collected, but there is a cost associated with each sample submitted so understanding where to focus sampling efforts can be a cost-effective way to help determine nematode species and populations.
Look for fields planted to cotton year after year.
Review yield maps for areas of the field with lower than expected yields.
Focus on areas of the field that looked stressed throughout the season.
Divide areas of the field based on soil type and previous crop history and sample based on areas with similar qualities.2
Soil moisture should be similar to conditions for planting—not too wet or too dry.
Time sample collection around harvest when nematodes are most active. Samples should be collected early in the week and sent either Monday or Tuesday so samples will arrive before the weekend.1
1. Use a soil probe to sample 8-10 inches deep (in the root zone) and within the row. Ideally, samples should contain soil and root fragments as some nematodes live within roots.
2. Collect one soil core per acre randomly throughout the field to be sampled. Combine 20 cores per sample. This should result in 1-2 pints of soil per 20 acres. Larger fields can be sampled based on soil texture, drainage, or previous crop.
3. Immediately place the sample into a plastic bag to conserve moisture and keep any nematodes present alive. Store the sample out of direct sunlight and in a relatively cool location, like an insulated cooler without ice. Do not refrigerate samples.1
4. Label each sample with the current crop, previous crop, planned crop, date sampled, location, and grower name.2
5. Send the room temperature samples to the nematology laboratory as soon as possible, ideally on a Monday or Tuesday to prevent samples from sitting in an un-airconditioned space over a weekend.1
Results from the lab will indicate the species of nematode present and the density of each species per 100 ml of soil. This information can be used with local threshold levels, which can vary based on soil type and species. Based on the species and population present, growers can determine if a resistant variety should be planted, if a nematicide should be used, and what cultural practices could be implemented to help decrease the potential for damage.1
1 Mueller, J., Kirkpatrick, T., Overstreet, C., Koenning, S., Kemerait, B., and Nichols, B. 2012. Managing nematodes in cotton-based cropping systems. Cotton Incorporated. https://www.cottoninc.com/wp-content/uploads/2015/12/2012-Managing-Nematodes.pdf.
2 Soil sampling to assess cotton nematode population distributions and densities. National Cotton Council of America. https://www.cotton.org/tech/pest/nematode/soil.cfm.
(Sources Verified 7/10/19)