November 14, 2002

Keeping Root Rot at a Minimum in North Dakota

The incidence of root rot in 2002 North Dakota wheat, durum, and barley was typical compared historically to other years according to Robert Stack, North Dakota State University professor of plant pathology. Statewide, the occurrence of root rot in wheat was around 6 percent, barley at 10 percent, and durum between the two.

"Root rot has had a presence in North Dakota since the earliest farming days", Stack explains. The fungus Cochliobolus sativus is the cause of this plague. C. sativus survives in soil or infected residue from previous crops. It can remain viable in soil for eight to ten years therefore making it unpractical to eliminate it from a field. Management must instead be used to control the occurrence.

The symptoms of root rot include brown spots and lesions on the sub-crown internodes and coleoptiles but also on the crowns and roots. Root rot damage is rarely recognized until severe damage has already been done. This is due to the fact that the destruction takes place at or below ground level. Many times it is mistaken for drought injury, soil problems, or weather damage.

According to Stack, if there is enough moisture in the ground for the crop to grow there is enough moisture for root rot to infect. The infection of crops takes place every year but the loss varies year to year due to conditions. Root rot thrives off stressful conditions. "The years with the greatest loss are those with cool, wet weather followed by hot, dry weather," Stack says.

Currently, NDSU is conducting studies to provide information on root rot resistance in previously released varieties of wheat and durum. Researchers are also screening advanced lines in NDSU’s breeding programs. The purpose of the screenings is to remove lines that are highly susceptible to root rot.

There are three high-risk situations where management should be considered to control root rot losses:

1. Growing a highly susceptible variety
2. Growing grain after grain
3. Growing on land with a history of root rot

Management techniques can help reduce the occurrence of root rot. Selecting a variety that has some resistance to root rot is recommended. Seed treatment can reduce root rot by up to 50 percent according to an NDSU study. "Crop rotation is the number one practical management technique," says Stack. He is very excited to see an increase in row crops in North Dakota over the past ten years. This is an indication of increased rotation programs.

According to Stack, the major economic cost from root rot occurs as the fungus nibbles away at 5-15 percent of a crop. Root rot also can cause reduced test weight or yield. "It is often overlooked because it rarely creates a dramatic loss," Stack explains.

If you would like more information on root rot there is a publication entitled Root and Crown Rots of Small Grains available through the NDSU Extension Service or on the world wide web at http://www.ext.nodak.edu/extpubs/plantsci/smgrains/pp785w.htm#Root.

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Contact: Robert Stack (701) 231-7077, robert.stack@ndsu.nodak.edu
Writer: Deana Oe (701) 231-8371, deana.oe@ndsu.nodak.edu
Editor: Tom Jirik (701) 231-9629, tjirik@ndsu.nodak.edu