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SOYBEAN CYST NEMATODE:
PUBLIC ENEMY #1 FOR SOYBEANS
Soybean Cyst Nematode (SCN) causes more economic damage than any other pest in U.S. soybean fields, costing the U.S. producer more than billion annually. Many producers are losing 15-30 percent of their yield to SCN without any above-ground symptoms. SCN has spread to almost all of the Midwest which leads some soybean experts to say there are only two types of soybean fields: those that have SCN or those that will get SCN!
The Soybean Cyst Nematode is a parasitic, microscopic roundworm that invades the soybean root’s vascular system as a juvenile. The female nematode stimulates a specialized feeding cell to form in the root and the nematode feeds from the cell, sapping the plant of nutrients and disrupting water uptake effecting plant growth. The female forms a tough egg sack (cyst) filled with 50-200 eggs that erupts through the root surface forming the white or yellow cyst on the soybean roots of infected plants. There can be 4-6 cycles of nematode development during a growing season, with a cycle completed in 24 days under warm temperatures.
IDENTIFY THE PROBLEM
The easiest method to check for SCN infestation is to check soybean roots from late June until mid August by digging the plant out of the soil with a hand spade and gently removing the dirt from the roots by shaking or by gently swirling in a bucket of water. Infected plants will have small white or yellow cysts about the size of a pin head on the root surface (considerably smaller than the nitrogen nodules). A soil sample can also be used to identify and quantify SCN infection. Collect the sample by normal soil sampling techniques mixing many cores due to the random distribution of the nematode in the soil and then send the sample to a qualified lab.
Using resistant varieties is the best method of managing nematode numbers and most universities recommend resistant soybeans if any soybean cysts are detected in the producer’s field. Genetic resistance involves three recessive genes and is very difficult to incorporate into soybeans. NuTech evaluates all cyst resistant soybeans it sells for cyst resistance by closely monitoring field trials grown in SCN infested areas as well as growing the soybeans in three different infested soils in the lab. These lab experiments allow the creation of a simple index to compare products. The lower the cyst index, the more resistant the variety. The cyst index is not an exact score but is a good indicator of resistance level.
Most Midwest universities have developed cyst nematode management systems for good SCN management for areas under heavy pressure or when new races have developed. These management systems deploy alternating crops and alternating SCN resistance varieties between the common PI 88788 cyst resistance source, Peking cyst resistance source, and SCN susceptible varieties. Alternating sources of cyst resistance is important in cyst nematode management systems and NuTech is one of the few companies with Peking source soybeans to utilize the cyst management systems.