Check for SCN in dried beans

Although the name “soybean cyst nematode” may be misleading, this parasitic worm infects both soybean and dried bean crops.

Sam Markell, plant pathologist at North Dakota State University Extension, explained SCN research and management techniques in a recent NDSU Extension webinar.

“It is very specific to dried beans and soybeans,” he said, noting that SCN does not affect other crop types. “The invader and equipment act on anything that moves the soil, such as water and wind.”

While it doesn’t affect dried beans as severely as soybeans, Markel said it can still cause yield reductions and damage, SCN said. Symptoms in affected dried bean fields will appear similar to soybeans, including stunted growth, poor canopy closing, and plants seen with fewer bean pods.

Some market grades of dried beans are more susceptible to SCN than others, and on average, no market grades are resistant, Markell said. “Dried beans, in general, are not as tender as delicate soybeans,” he said. “We don’t have a lot of beans that we think are really hardy, but the majority of them will be moderately resistant.”

In soybean, resistant varieties are offered to producers.

Scout and example

Soil sampling and testing show SCN populations approaching the country of beans. “If you’re growing beans, you probably want to start sampling,” Markell said.

He recommends that manufacturers in east-central and southeastern North Dakota incorporate SCN sampling into their crop management practices.

Any bean field with an SCN usually doesn’t show above-ground symptoms until it becomes a bad infestation, Markell said. “It’s a parasitic worm and it lays eggs,” he explained. “If you can count the eggs to find out how many eggs are in the soil, you can control what your risk is.”

Since the parasite lives in the roots, in-depth sampling is not required for SCN. “Aim for the root; All you need is 6 to 8 inches,” Markell said.

A soil probe can be used that takes samples directly from rows near plant roots. To sample properly, take 15 to 20 1-inch diameter soil cores 8 inches deep. Cores should be collected in a zigzag or “M” shape for better testing.

Producers can also check for SCN by gently digging up the plants and checking for white or yellow cysts on the roots. Cyst control can begin five to six weeks after planting and continue until late July or early August.

He recommends sampling close to harvest time, focusing on areas that are potential hotspots for SCN. “Focus on where the new soil is more likely to move,” he said. “Field entrances from equipment, bunker belts if we get strong winds – wherever the ground moves.”

If you do detect SCN in your fields, the best methods of managing it include rotation to non-host crops, planting SCN resistant soybean varieties, or using nematode prophylactic seed treatment. Contact your agronomist or county Extension office for more specific management tools.