, Farm Journal Seeds & Production Editor
Fall soil sampling is the first step to a soybean cyst nematode (SCN) management program and the best way to prevent potential losses from the pest the following season, says Greg Tylka, an Iowa University Extension plant pathologist.
Results will indicate if fields are infested with SCN or if SCN population densities are being kept in check in infested fields that have had SCN-resistant varieties grown in the past. "You can continue to sample for SCN into the winter months as long as the ground is relatively dry and not frozen. We do suggest avoiding muddy conditions,” Tylka says.
Need to sample for corn nematodes? Fall and winter is not a good time to collect soil samples to check for these pests. Corn nematode populations typically decrease in the latter part of the growing season. And it is not possible to calculate what the numbers were in the earlier part of the growing season. Therefore, low corn nematode numbers obtained from fall soil samples are not very informative, Tylka says.
If population densities of corn nematodes are high in soil samples collected in the fall, it is safe to assume that the numbers were high earlier in the season, as well.
The exception are needle and sting nematodes. These species live only in soils that are at least 70% sand, and they migrate down into the soil profile during the heat of summer. So they are best detected in spring or fall soil samples.
Guidelines for Collecting Soil Samples to Test for SCN
- Samples should be collected using a soil probe.
- Soil cores should be collected to a total depth of 6" to 8".
- Collect soil cores from 15 to 20 places in a zigzag pattern within a sampling area.
- Collect a separate set of soil cores for each 20 acres or so.
- Combine and mix soil cores, and fill each sample bag with one cup or more of soil.
- Label the outside of each sample bag with a permanent marker.
- One sample can be used to test for SCN and for nutrient analysis.