WOOSTER, Ohio – Harvesting corn and soybeans may be the only thing on the minds of Ohio growers at the moment, but they shouldn't overlook the importance of soil testing for soybean cyst nematode.
Soil sampling in the fall is the first step to a soybean cyst nematode management program and the best way to prevent potential yield losses from the pest the following growing season, said Ohio State University Extension program specialst Dennis Mills.
"The best way to manage SCN is to know which fields have nematodes and how many nematodes are present," said Mills, who also has an appointment with the Ohio Agricultural and Research Development Center. "Sampling in the fall will give an estimation of the population level on which to base management decisions for planting next spring."
Mills said soil sampling is inexpensive, quick and easy, and is an accurate representation of any SCN activity in a grower's field. In order to prepare a soil sample, growers should follow these guidelines:
• Use a 1-inch diameter soil probe to collect soil samples (6-8 inches in depth).
• Following a zigzag pattern, collect 10-20 soil cores per 10-20 acres.
• Collect cores from areas of similar soil type and crop history.
• Dump cores from each 10- to 20-acre area into a bucket or tub and mix thoroughly.
• Place 1 pint (2 cups) of mixed soil in a soil sample bag or plastic zippered bag and label with a permanent marker.
• Store sample in cool, dark place until shipping.
• Send the composite sample to a lab doing SCN analysis, such as the C. Wayne Ellett Plant and Pest Diagnostic Clinic (http://ppdc.osu.edu).
Mills said that growers should take great care when preparing soil samples. Several environmental and biological factors exist that can cause variability of SCN populations and yield inaccurate sampling results. Such factors include SCN population patterns, soil structure, cropping history, timing of egg hatch, survival tactics, tillage, and the presence of alternate hosts.
Yield loss threshold of SCN in Ohio begins at 200 eggs per cup of soil. At 2,000 eggs per cup of soil, most susceptible soybean varieties suffer significant economic losses. At 5,000 eggs per cup of soil, growers should avoid growing soybean varieties altogether, even resistant varieties.
"The take-home management message is rotation, rotation, rotation," said Mills. "It's the most effective way of controlling SCN."
Currently, SCN is present in the majority of Ohio counties. Once infestation takes hold, it's almost impossible to rid the pest from a soybean field without intensive management practices.
Deemed the "silent robber of yields," SCN is the No. 2 soybean pest in Ohio, behind Phytophthora sojae, which causes Phytophthora root rot. Soybean cyst nematodes feed on the roots of young plants, which prevents the roots from taking up vital nutrients. The result is a drop in yields and subsequent economic losses.
For more information on SCN management, refer to the Ohio State University Extension fact sheet, "Soybean Cyst Nematode," at http://www.oardc.ohio-state.edu/ohiofieldcropdisease/soybeans/AC_39_08.pdf.