If you didn’t sample for soybean cyst nematodes in the fall as recommended, you can still collect soil samples for SCN. We have been talking about this at Extension meetings and thought it would be good to review how and where to sample. Here are some of the questions and answers from the winter meetings.
1) Which fields should I target?
If you have never sampled your fields before, here are a few characteristics that we have found to be associated with high numbers of SCN: low yields – those fields which are off the county average by 5 to 10 bu/A; fields that have been in continuous beans; fields that do not mature evenly, pockets that mature early, presence of sudden death syndrome. Soybean yield from fields with SCN is highly variable, there will be high and low spots associated with the high and low numbers of SCN. Target those areas where the yield maps are showing low yields.
2) How to collect the soil sample?
Collecting soil for SCN sampling is similar to collecting for a soil fertility sample. The top 6 to 8 inches of soil, sample in the row and not between the rows. Walk in a Z or W pattern, collect cores in a bucket. Mix them thoroughly and send a good quart bag size (labeled with a permanent marker with your name and location) to the SCN testing lab of your choice.
3) Where do I send them?
There are a number of labs that process SCN soil samples and they are listed here:
OSU C. Wayne Ellett Plant and Pest Diagnostic Clinic
8995 E. Main St. Bldg. 23
Reynoldsburg, OH 43068
Brookside Laboratory Inc.
200 White Mountain Drive,
New Bremen, OH 45869
2685 CR 254
Vickery, OH 43464
Spectrum Analytic Inc.
1087 Jamison Rd. NW
Washington Court House, OH 43160
4) What do the numbers of cysts/eggs mean?
First, this number is an average and an estimate of the number of SCN eggs or cysts within a cup of soil. SCN populations are highly variable, so we use this number to assess risk and make management recommendations.
5) What if my numbers are high, but I’ve been growing SCN resistant varieties?
This is a good indication that SCN has adapted to SCN resistant varieties. Most resistant varieties have the same source of resistance (PI 88788), so selection pressure is high for SCN that can break resistance. To get the numbers down, rotate to a nonhost crop for two to three years, then find a variety with a different source of SCN resistance, such as Peking (the source of resistance should be listed in variety descriptions from the seed company or from the seed dealer). Recheck the SCN numbers before planting soybeans, and don’t include susceptible soybeans in your long-term rotation. Be sure to use a different resistant variety for each soybean rotation.