Fall is a perfect time to sample fields for the presence of the soybean cyst nematode or SCN. Knowing if SCN is present and at what population densities will increase the chances of profitable soybean production in 2014. That's the advice of Greg Tylka, Iowa State University Extension nematologist and plant pathologist.
"As we work to complete harvest and put the finishing touches on the 2013 growing season, it is not too early to start thinking about 2014 crops," he says. "Results of soil samples collected in the next few weeks from fields in which soybeans will be grown in 2014 could mean the difference between 'so-so' and profitable yields next year."
The soybean cyst nematode is a widespread pest of soybeans in Iowa and the Midwest, and SCN reproduction was extremely high in the 2012 growing season. "Many of the fields in which soybeans were grown in 2012 will be planted to soybeans again in 2014," says Tylka. He provides the following observations and suggestions.
Fall is a perfect time to collect soil samples to check fields for SCN and to determine the population density (number) of SCN in the fields, if it is present. If SCN is discovered at low or moderate population densities, SCN-resistant soybean varieties should be grown in 2014 to maximize soybean yields in the presence of the nematode.
Fall also is a good time to determine if SCN was present in soybean fields in 2013. Collecting samples for this purpose is done in the same manner as sampling fields of corn stalks for SCN in anticipation of the 2014 soybean crop. Following are some sampling guidelines.~~~PAGE_BREAK_HERE~~~
How to collect a good sample
Collect 8-inch-long soil cores.
Collect 15 to 20 soil cores per sampling area.
Limit the area sampled to 20 acres or so, if possible.
Collect numerous multiple-core samples from different areas in large fields
If grid sampling, collect one or two soil cores from every grid cell and combine cores from the number of cells that represent approximately 20 acres.
Collect cores from underneath crop row if soybeans were grown this season.
Do not collect samples if the soil is muddy or frozen.
Send samples to a private soil-testing laboratory that does SCN testing or to: Plant and Insect Diagnostic Clinic, Iowa State University, 327 Bessey Hall, Ames, IA 50011.
Soil sampling pattern based on the agronomic features of the field.
SCN decrease yields substantially without showing obvious above ground symptoms on soybean plants. Soil sampling strategies for SCN vary, depending on the history of the pest in the field. In fields without symptoms or known history of SCN, ISU agronomists suggest soil sampling in the fall, which is when SCN numbers are highest.
For growers without a known SCN problem, sampling fields without symptoms every 4 to 6 years is the only way to detect these pests before becoming an economic problem. When sampling, target areas likely to be introduction points for SCN such as entryways, fence lines, areas prone to flooding, and consistently low-yielding areas. SCN requires a combination of strategies for effective control. Soil sampling, clean equipment, crop rotation and planting SCN resistant soybean varieties will help protect against SCN. Additional management practices — such as avoiding low fertility, compaction, drought stress and other disease or insect pressure — promote good soybean health and enable plants to better withstand the effects of SCN.
More information on SCN: For more information about the biology and management of SCN, visit the SCN page of ISU's Plant Pathology and Microbiology Department and the North Central Soybean Research Program website.