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Posted 28 January 2015. PMN Crop News.

Controlling the Harmful Effects of Nematodes

Source: United Soybean Board Press Release.

Chesterfield, Missouri (January 13, 2015)--According to Terry Kirkpatrick, nematodes have become a fact of life for soybean farmers. These yield robbers might be here to stay, but that doesn’t mean farmers are helpless to control them.


Fields with nematodes typically produce smaller yields and also have problems with weed management. Just one member of the nematode family, the soybean cyst nematode (SCN) costs U.S. soybean farmers over $1 billion in yield losses annually.

Kirkpatrick, Ph.D., a professor at the University of Arkansas, says farmers shouldn’t try to eradicate nematodes, which would be practically impossible. Instead, they should aim to control their numbers so that their harmful effects on soybean crops are negligible.

“We’re never going to eradicate it from a field, and we don’t need to,” he says. “What we need is to keep it from costing as much.”

Managing nematodes

A farmer’s best tool against nematodes is seed varieties with resistance to these pests. However, different varieties offer resistance to different nematode types, so a farmer needs to know which type lives in his or her field.

“The day a seed is planted in a field is the last day the farmer has to manage a nematode problem that year,” he adds.

Kirkpatrick supervises the Arkansas Nematode Diagnostic Laboratory, which can analyze soil samples submitted by farmers to identify the type of nematodes afflicting their farms, as well as their magnitude. Similar facilities exist in other soybean-producing states.

“You’ve got to know what nematodes you’ve got, you’ve got to know where it is, and you’ve got to know how bad it is,” says Kirkpatrick. “The question is: How many really bad spots with high population densities in the field do I have? One spot, not a big deal. Forty percent of the field with a nematode problem? That’s severe. That’s a big deal.”

Hear more from Kirkpatrick about his nematode research.

Checkoff-funded nematode research

The soy checkoff funds research to help farmers overcome production challenges, such as nematodes and other pests and disease.

The Arkansas Soybean Promotion Board (ASPB) sponsors a statewide survey on past, present and future soybean fields to determine the best methods for controlling nematode populations. ASPB also funds work on new nematicides and studies to identify which crop-rotation programs work best at managing nematodes.

Learn more from the checkoff about managing nematodes, including more tips to control SCN and the link between SCN and aphids.

Types of nematodes

Kirkpatrick says the three types of nematodes that cause problems in Arkansas soybeans include:

1. Root-knot nematodes – The most destructive to Arkansas soybean plants.

2. Soybean cyst nematodes – A problem for many years in Arkansas and the biggest nematode issue in most other soybean-producing states.

3. Reniform nematodes – A relatively new species of roundworm in Arkansas that has surfaced over the past 20-30 years and mainly attacks cotton plants. As cotton acreage shrinks in Arkansas, these nematodes now feast on soybeans planted in the same space. The effects of these nematodes on soybean crops are still unknown.

“Nematodes are parasites,” he says. “They are a little bit like mistletoe on an oak tree. It’s not to their advantage to kill the crop outright. They need to have a living host to complete their lifecycle.

According to Kirkpatrick, root-knot nematodes create lesions on soybean roots, which make it difficult to efficiently transport nutrients and water up the stalk, resulting in shorter and yellower plants.

He also notes that nematodes are not mobile, but spread to new locations via dirty equipment, such as muddy tires, or through infected plant material. Otherwise, infestations expand at a rate of only three to four feet per year.

Courtesy Arkansas Soybean Promotion Board. Be sure to watch Field to Film, ASPB’s series of soybean-research videos.