Production Blog

Don't Feed the Nematodes

Pam Smith
By  Pamela Smith , Crops Technology Editor
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Go ahead and cover up with crimson clover. It's one of the cover crops that is a poor host for SCN. (DTN photo by Pamela Smith)

DECATUR, Ill. (DTN) -- Cover crops have many agronomic incentives, but researchers urge some caution about what you seed if fields are infested with soybean cyst nematodes (SCN).

It turns out some cover crops have the potential to become SCN hosts. While many of the most common cover crops get a thumbs up and aren't thought to cause problems, there are a lot of new crops being suggested, especially as cover crop seed gets tight.

Researchers with The SCN Coalition have compiled a list of cover crops that are suitable to grow in SCN-infested fields. The list is based on the results of checkoff-funded research published by Iowa State University and North Dakota State University.

"If you have SCN in your fields, we encourage you to consider cover crops that are nonhosts and poor hosts for SCN," said George Bird, Michigan State University nematologist and leader of The SCN Coalition in a news release. "It's the single most damaging pest in North American soybeans, and once it's in your fields, you can't eliminate it completely, but you can manage it."

Legumes (nitrogen-fixing) that are poor hosts or nonhosts for SCN:

Alfalfa

Austrian winter pea

Berseem clover

Cowpea

Crimson clover

Hairy vetch

Peas

Red clover

White clover

Researchers at North Dakota State found slightly higher SCN reproduction on Austrian winter pea, hairy vetch and field peas than what Iowa State scientists found, but reproduction was low in both studies.

Grasses and cereal grains that are poor hosts or nonhosts for SCN:

Annual ryegrass

Barley*

Cereal rye

Oats*

Wheat*

*From the SCN Management Guide 5th edition

(https://soybeanresearchinfo.com/…)

Brassicas (radishes, cabbage, mustards) that are poor hosts or nonhosts for SCN:

Canola

Daikon-type radish

Mustard

Oilseed radish

A good example of how it would be easy to feed the nematodes is recent discussions of planting field pennycress as a cover crop, which is also in the Brassica family. Studies at Purdue University show that field pennycress is a moderately good host for SCN, Bird noted.

He also warned that reproduction of the nematode on field pennycress could lead to increases in SCN population densities and recommended avoiding it as a cover crop in SCN-infested fields. Purdue has also established that winter annual weeds, such as henbit and purple deadnettle, can be SCN hosts.

The United Soybean Board, North Central Soybean Research Program and several state soybean boards are supporting research on cover crops and SCN. The SCN Coalition has also stated that there is no published research available yet showing that cover crops can consistently reduce SCN populations.

"The problem is, SCN eggs in their mother's protective cyst can remain viable in the soil for more than a decade," Bird said. "So we're also looking at new approaches, including biological controls and trap crops, which are crops that attract nematodes but aren't suitable hosts.

"For the past five years, my laboratory at Michigan State University has been searching to discover the first trap crop for SCN. We hope that our 2019 fall-planted cover crop, followed by a 2020 soybean crop, will identify the first true trap crop for SCN," he said.

Bird also reminded farmers that all varieties of the same cover crop are not created equal. "Select the best variety to meet your objective and manage it to achieve your objective. Specific details about using cover crops in SCN-infested fields in your area can be obtained from your state Extension nematologist."

The SCN Coalition is a public/checkoff/private partnership formed to increase farmer involvement in actively managing SCN. For more information go to: https://www.thescncoalition.com/…

Iowa State research can be found here: https://www.researchgate.net/…

North Dakota State University research can be found here: https://www.researchgate.net/…

Purdue research on winter annual weeds is located here: https://www.soybeanresearchinfo.com/…

Pamela Smith can be reached at pamela.smith@dtn.com

Follow her on Twitter @PamSmithDTN

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Pam Smith