NDSU Extension - Griggs County

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September 7

The Extension Connection

By Megan Vig

NDSU Extension and the North Dakota Soybean Council are working together again to coordinate a soybean cyst nematode (SCN) soil testing program.  A total of 2,000 soil testing bags will be available at county extension offices across the state on a first come first serve basis.  Soybean producers can obtain up to three bags each.  Each bag is pre-marked with billing information that will be covered by the North Dakota Soybean Council from checkoff funds.  To submit a sample, fill the bag with soil, provide site information and send the bag to the partner lab (Agvise).  Results will be mailed directly to the growers who submitted the samples.

                This SCN sampling program began in 2013 and has been instrumental in understanding where SCN is located in the state.  To date, over 3,000 samples have been submitted by North Dakota growers, and about 1/3 of those have had some level of nematode eggs.  The egg levels and geospatial positions from previous years’ samples that were used to general SCN distribution maps in North Dakota show “hot spots” in much of the southeast and movement to the north and west.  NDSU does not have access to any personal information; only the egg level and geospatial data to generate these maps.   

                Sampling in the fall is when SCN egg levels are highest, and consequently the most likely time of year to detect SCN.  Sampling can be done before or after harvest, but should be done before any tillage is done in the field.  Sampling is most effective when the sample is collected within a few inches of the soybean stem and 6 to 8 inches deep into the soil.  Samples should be kept relatively cool and sent to the lab quickly.  Do not let the sample sit on the dash of a pickup in the fall sun. 

                SCN moves with the soil, so consider the most likely way SCN-infested soil might be brought into a field.  Additionally, consider “suspicious” areas.  The most important areas to sample include the following. 

Field entrance: SCN-infested soil often moves into new fields on equipment.  Movement on equipment is the most common way the pathogen transfers and is thought to be responsible for its expansion across the U.S. 

Flood-prone areas and low spots: cysts will move with water, so areas that are prone to flooding and water pooling are likely areas where SCN will be introduced.  SCN can be moved by birds, on their bodies and in their digestive tracts; birds frequently visit wet spots in fields. 

Shelter belts: cysts can move in dust storms or high winds and are deposited as the wind speed slows.  In North Dakota this usually means shelter belts. 

Yellow spots showing up in August: the damage from high SCN levels usually begins to appear in August, especially in plants that are water-stressed.  Any lens-shaped areas of fields turning yellow in August are suspicious. 

High pH: high pH soils are very favorable to SCN and SCN is often noticed first in high pH spots in fields. 

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