by Dr. Charla Hollingsworth, U of MN Extension Plant Pathologist
In 1954, the first detection of the soybean cyst nematode (SCN) occurred in North Carolina. Since that time, the nematode has become the most important disease issue of soybean in the world. Spread with soil, this microscopic roundworm continues to gain ground in Minnesota soybean-producing areas. Essentially anything that can move small particles of soil will also transport this nematode.
Once considered a southern Minnesota problem, in recent years the nematode has established in fields located in the southern Red River Valley. Just like an Alaskan gold digger, the worm is dogged in its northward progress into the RRV. How soon it will be detected north of Clay and Becker Counties is anybody's guess, but its means of transportation is not as uncertain.
The primary vehicle of transport for the SCN will likely be by truck (Figure 1). Dumping tare soil onto fields that originates from unknown field locations is an effective mechanism for introducing the nematode into non-infested locations. Routine tillage activities after the introduction then function to spread SCN throughout the field. Another fairly common means of spread is through using farm equipment in an infested field followed by a non-infested one. Soil clinging to cultivators, planters, diggers, etc. can contain SCNs and effectively move the pest from one location to another.
Information is Power
Knowing whether the SCN is in your field is an important first step in minimizing its spread on your farm and being able to manage the disease. Aboveground symptoms are not always obvious and can look like other environmental stresses caused by iron chlorosis and saturated soils. Once detected in your field, educational opportunities should shift from preventative in nature to those associated with management strategies aimed at preserving bean yield and quality. This disease cannot be eradicated from a field after it arrives, so knowing effective disease management strategies will be very important for Valley producers.
Disease Detection is a Good First Step
University of Minnesota Extension professionals may be contacting you soon. A targeted field survey for SCN will be conducted over the next 1 - 2 months to determine the extent of the nematode's distribution in the RRV. This research effort is being funded by the Minnesota Soybean Research and Promotion Council and is made possible by your soybean check-off.
Extension personnel are looking for high risk fields to survey. These consist of fields that were worked using farming or plot equipment that is also used in more southern, SCN-infested areas. Those fields in which sugar beet or potato tare soil is dumped will also be targeted. If this describes one of your fields, please contact either Hollingsworth or the extension educator in your area. Contact information for key researchers is listed below.
After candidate high-risk soybean fields are identified, surveyors will collect soil samples that will later be processed and analyzed at the U of M's Nematology Lab located near Waseca at the Southern Research and Outreach Center.
New Disease Detections?
If the nematode is confirmed in counties that were previously thought to be non-infested, U of M Extension and Minnesota Department of Agriculture personnel will work cooperatively to notify and educate growers about the effects of SCN.
The results of this survey will be delivered to the agricultural community by participants as soon as the project is completed. Until then, please be aware of the risks involved with transporting soil from one field to another.
Those actively involved in the SCN survey effort are: