By JEFF BURBRINK

Extension Educator Purdue Extension

Jeff Burbrink

GOSHEN — I have talked to a number of producers this fall about soybean yields that fell short of their expectations. In most cases, soybean cyst nematode (SCN) is believed to be the issue.

One thing I have learned from these conversations is that while most growers are sure they have SCN, many have never tested for them. It is not a bad assumption, because most fields probably do have numbers of SCN that can cause yield reductions.

However, around the Corn Belt, researchers are seeing a buildup in SCN numbers, even where SCN resistant varieties are being used. Use of resistant varieties is the most common and economical way of managing this nematode. However, the source of resistance for almost 97% of the current resistant cultivars is the same genetics (PI 88788), and it appears that SCN is adapting quickly to this characteristic. So, just knowing how many SCN are in the field, and using a resistant variety might not be enough information.

If the PI 88788 resistance has been used in a field more than 5 times, there is a good chance the SCN have begun to adapt. In that case, soybean growers should be submitting samples to labs that can test the type of SCN population present.

If there is a pattern of poor soybean growth, or an unexplainable low yield, or if SCN is known to be present in nearby fields, soil samples should be collected from a depth of 6-8 inches in a zig-zag pattern across the field and sent to a nematology laboratory for analysis.

Place the sample, consisting of at least a pint of soil, in a plastic bag and close with a rubber band or string tie. Attach to the outside of each bag a label identifying the sample. If you do not have a specific problem area, collect small amounts of soil (with a probe or trowel) from the entire field.

A number of universities in the Midwest can type test SCN. There are also private laboratories that can test for SCN types. Ask if your lab can measure the ability of the SCN population in your soil to develop on a susceptible variety and the three commercially available sources of SCN resistance: PI88788, PI548402 (Peking) and PI437654 (CystX or Hartwig).