How do I take soil samples for detecting the soybean cyst nematode?
Soil sampling is an efficient way to determine if SCN is present in a field when SCN is suspected but cannot be observed on roots. This type of sampling can be done at any time of the year when the physical conditions of the soil will permit use of a soil sampling tube or, less desirably, a shovel.
A sample consisting of 10 to 20 one-inch diameter by 6-8 inch long cores should be collected from each of several localized "most likely" sites in a field. One "most likely" site would be a short distance from entry point where tillage equipment enters the field because contaminated equipment is the number one method by which SCN is introduced into a property. Infested soil scoured from equipment at such locations allows SCN buildup to begin there. Another "most likely" site would be on the leeside of a small hill or knoll, or along a fence or tree line. Wind-blown soil containing cysts tends to settle out at such locations much like wind-driven snow accumulates behind a snow fence or similar obstacle. A third "most likely" sampling site would be low areas that flood when streams overflow. Egg-filled cysts can be carried and spread by moving water.
In addition, soil cores should be collected from in-row locations rather than from between crop rows that are 15 inches or more apart because nematode populations are much more likely to be larger in soybean rows than they are between the rows where plant roots are scarce.
Soil samples enclosed in individual sealed plastic bags should be submitted to a professional laboratory for processing. Although the dark brown cysts can be seen with the unaided eye, they are very inconspicuous when mixed with soil. The laboratory will use a procedure to "float" any cysts out of a soil sample. Eggs, if any, will be released from the cysts, and counted. The lab's report will report number of eggs per 100 cm3 (approximately one-half cup) of soil.