GOSHEN, Ind. — Soybean cyst nematodes (SCN) are a big problem for local growers. They are capable of reducing bean yields by 50%, and are reportedly in more than two-thirds of our local fields.
Symptoms of SCN injury can easily be confused with other problems such as nutrient deficiencies, herbicide injury, disease, and poor drainage. In fields recently exposed to SCN, the pattern tends to follow the rows, with oblong areas of stunted, yellowed plants. This pattern is caused by tillage equipment dragging the cysts to new locations in the field. While not limited to sandy, irrigated fields, they certainly seem to thrive there.
Symptoms are generally more pronounced when soybean plants are under stress from such conditions as drought, low fertility, or compaction. Infected plants have poorly developed roots and very few Rhizobium nodules. Early in the growing season (6 weeks after planting), close examination of the roots may also reveal small, white to yellow spheres (bodies of female nematodes) attached to the root surface. These females are not much bigger than grains of coarse sugar, and should not be confused with the much larger Rhizobium nodules.
Purdue recently hired a nematologist, Dr. Zhang, to focus on resistance management with SCN. We are providing FREE soybean cyst nematode (SCN) soil testing to Indiana growers with support from the SCN Coalition and National Soybean Board. If you have some trouble fields and you have not had a recent SCN test, please consider sending a soil sample to Purdue this fall.
The equipment you need for sampling soil for soybean cyst nematode is the same equipment you use for taking a soil sample for soil nutrient analysis: a soil probe, a bucket, and a plastic soil bag.
To collect soil samples for SCN diagnosis, we recommend you collect 10 to 20 of cores of soil, each with 1 inch-diameter and 6 to 8 inches-depth in a 20-acre area. If the field is larger, break the field into 20-acre units and take 10 to 20 cores per unit.
Take cores from within root zones and use a zig-zag or M-pattern to collect soil cores. In addition, you may also want to include samples from a high-risk area, such as near a field entrance, areas where the yield seems to be a little lower than the last time soybeans were grown, or along fence lines where wind-blown soil accumulates.
Bulk the cores in a container and mix thoroughly. Take the time to mix the sample. The better the sample is mixed the better it represents the whole field. Put 1 pint of the thoroughly-mixed soil in a plastic bag and label it with a permanent marker. Don’t put a paper label inside the bag. The moist soil will make it unreadable by the time the sample reaches the lab.
For accurate results, keep the soil sample at room temperature or cooler and keep out of the sun or hot truck cab until you are ready to pack and ship it. Pack the samples in a box and cushion the samples with packing material so the bags don’t break open during shipping. Label each sample with your name, address, phone number and email address, and the name of the field the sample represents. The form to accompany the samples can be downloaded from this link: shorturl.at/loGS5.
The samples should be shipped to:
Purdue Plant and Pest Diagnostic Laboratory, LSPS-Room 116
Purdue University
915 W. State Street
West Lafayette, Indiana 47907-2054
— Jeff Burbrink, Extension Educator, Purdue Extension Elkhart County
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