July 13, 2007

It may not be as prestigious as a Master Angler bass or a Boone & Crockett buck, but a Cuming County soil sample submitted to the UNL Plant and Pest Diagnostic Clinic shattered the old state record for soybean cyst nematode (SCN) egg counts. There were 136,000 eggs in 100 cc's of soil (approximately 4 oz of soil).

A sample with a high SCN count coming from Cuming County is significant for two reasons. First, SCN wasn't detected in Cuming County until 1998, 12 years after it was first found in Nebraska. Second, it is not a county bordering the Missouri River. The earliest detections and highest counts were generally found in the Missouri River valley.

Some soybean producers and field scouts still think of SCN as an eastern Nebraska problem; however, this pest has been identified in 41 counties producing three-fourths of the state's soybeans. SCN has been identified as far west as Boyd, Valley, Buffalo and Kearney counties.

Often SCN can reduce yields by 20-30% with no visual symptoms on the plant. This summer's dry weather has altered that usual pattern. Sometimes, but not always, areas in soybean fields infested with SCN can be identified by stunted or wilted plants. Although other stresses may cause similar symptoms, the combination of SCN damage and dry conditions is making SCN infestations more pronounced and easier to identify.

Normally we recommend sampling for SCN after harvest but before fall tillage. It is easier to get around in fields then and poor yielding spots are fresh in your mind. This year it may be a good plan to sample suspect areas in a field while the crop is growing and stressed plants may be more obvious. Unlike most other pests, you can sample for SCN any month of the year.

Soybean Board Support for Testing

When sampling fields for SCN, be sure to take advantage of an SCN scouting program supported by the Nebraska Soybean Board). Bags for a free SCN test (a $20 value) are available at your UNL Extension office or from the Department of Plant Pathology. This program is in its third year and has helped define the distribution and frequency of SCN in Nebraska soybean fields.

In the first two years of the project, about one-fourth of the samples came back positive for SCN. While these weren't random samples, it does show that SCN is more common than we might expect. In many cases the growers had no idea they had SCN in the fields that were sampled.

UNL Extension and the Nebraska Soybean Board have partnered to assist soybean producers, field scouts, crop consultants and other agronomic professionals learn more about identifying and managing SCN. Four SCN Field Days will be held in August. More information will be available in CropWatch later, but be sure to mark your calendar with the date of the field day nearest you.

• Tuesday, August 21, 3 p.m. near Concord
• Wednesday, August 22, 10 a.m. near Newman Grove
• Wednesday, August 22, 6:30 p.m. near Plainview
• Friday, August 31, 9 a.m. near Mead

Last year field days were held at four sites with low to moderate levels of SCN. At these four sites, SCN-resistant varieties outyielded comparable susceptible varieties by an average of seven bushels per acre. The same varieties were planted at a non-infested site and there was no difference in yields between resistant and susceptible varieties.

To learn more about identifying and managing SCN and how it can impact your yields, make plans now to attend an SCN Field Day near you in August.

John Wilson
Extension Educator
Loren Giesler
Extension Plant Pathologist, Lincoln