NDSU Extension - Griggs County


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October 30

Extension Connection column by Jeff Stachler

Soybean Cyst Nematodes

Hello.  Corn harvest in the county is at least 85% completed as of last Friday.  The weather looks good to  finish if there is any left to harvest.

Soybean cyst nematodes (SCN) are becoming more prevalent in Griggs County and North Dakota!  Current testing results since 2013 indicate about 26 samples have been submitted from Griggs County.  Only about 15% of those samples have tested positive for the presence of SCN eggs in the soil.  Of those samples testing positive, the number of eggs in the soil has been from 50 to 200, a very low level.  At this level it is possible to have a false positive or just a very low level, so sampling in the future is very important to catch changes in the population.  Higher levels of SCN egg counts have been found in Steele and Barnes Counties, so it is getting closer!  There are soil samples in Steele County having 20,000 or more eggs per 100 cc of soil which is extremely high and causing substantial yield loss.  SCN is the top yield-robbing pest of soybeans in the United States.

SCN is a big problem for dry bean and soybean production!  Pinto and navy beans are the most commonly grown dry bean in Griggs County.  Pinto and navy beans are moderately susceptible or susceptible to SCN and some soybean varieties are susceptible to SCN.  Besides soybean and dry bean, some weeds like purple deadnettle and henbit are also hosts to SCN.

SCN is a nematode which is a microscopic worm that feeds and reproduces on root tissues.  There are three stages of development, egg, juvenile, and adult.  Only the juvenile attacks the roots of plants.  Female worms enter the roots and begin producing eggs.  As they produce eggs their body expands into a lemon-shaped structure called a cyst which is visible with the naked eye.  These cysts are very resilient to soil and weather conditions allowing them to remain protected over the winter and potentially for several years!  Each female can produce a couple hundred eggs.  The life cycle lasts for about 24 to 30 days so two to three generations are possible during a growing season causing egg counts to rise quickly.  The presence of SCN makes sudden death syndrome more prevalent.

Management of SCN must be finalized before planting.  The only management options are to keep equipment free of soil, rotate away from soybean and dry bean, plant resistant varieties, and apply seed treatments which have been variable. 

It is difficult to know when you have SCN as there are no good unique characteristics.  Yield loss due to SCN has been mistaken for things such as compaction, iron deficiency chlorosis and other nutrient deficiencies, drought stress, herbicide injury, or other plant diseases.  The only way to know if you have SCN is to test the soil for the presence of eggs.

The North Dakota Soybean Council is sponsoring a soil sampling program for SCN.  The testing fee is free to farmers.  All you have to do is stop by the Extension Office to pick up some soil sample bags.  You may pick up three bags at a time.  As the weather will be warming back up again now is an excellent time to take these soil samples.

Before sampling, fill out the sample bag with all of the desired information, especially the GPS coordinates for one of the soil cores.  Take 10 to 20, 1 inch soil probe core samples to a depth of 6 to 8 inches.  Insert the soil probe next to an old soybean plant targeting the area with the most roots.  Crumble the soil cores and mix the soil thoroughly then fill the sample bag.  Sample the following areas of the field:  field entrances; low spots where water pools; frequently flooded areas; along shelter belts or fence lines; high pH spots in the field; and areas having unexplained yield loss.  Keep the soil samples in a dark and cool place until shipping them to Agvise at 604 Highway 15 West, P. O. Box 510, Northwood, North Dakota 58267. 

Here are some short videos you can look at to learn more about soybean cyst nematodes https://www.thescncoalition.com/lets-talk-todes


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