Greg Tylka says farmers routinely ask him what they can do mid-season to address soybean cyst nematode (SCN) pressure.
His traditional response over the years has been, “Not much.” But that’s changing, thanks to a new partnership between the SCN Coalition and Valent. The two have teamed up to launch a new educational program, SCN Root Check, to help farmers better address the pest.
SCN is the leading yield-robber of North America’s soybean crop, causing more than $1.5 billion in annual losses. In severe cases, the pest can destroy 80% of a field’s yield potential. University of Illinois research shows that when SCN goes undetected in fields it can still sap yields by up to 30%.
The partners are urging farmers to check soybean plants between now and early September and count how many female SCNs are present on plant roots.
There are two methods farmers can use to evaluate the presence of SCN, in addition to soil tests, according to Tylka, Extension nematologist and professor at Iowa State University and director of the Iowa Soybean Research Center.
Consider high-risk areas in fields. “Look (at soybean plant roots) in field entryways, high pH spots, low spots where water washes, and in areas along fences where windblown soil accumulates,” he advises.
Often, though not always, circular areas of stunted, yellowed plants can be observed where SCN is present.
Option No. 2: do routine checks in fields where soybeans are planted or will be planted. “SCN is one of those problems that is so insidious that any field should be checked,” Tylka advises. “I tell people to carry a spade with them routinely and as they’re walking through soybean fields, stop every 100 paces, dig some plants and look the roots for the presence of the females.”
The females will appear as small, cream-colored roundworms, approximately the size of a period at the end of a sentence in a newspaper or book.
“They are visible to the unaided eye for most people, but if you have poor near-sighted vision, you might want to use a magnifying glass or hand lens to look for them,” Tylka says. “The females are much brighter and smaller than the normal nitrogen fixing nodules that we expect to see on healthy soybean roots,” he adds.
Dig, don’t pull. Tylka emphasizes that farmers need to dig up soybean plants with a spade or shovel to evaluate the roots. Don’t pull up the plants, because that could dislodge any female SCNs present and affect your count.
Because the number of SCN can vary widely within a field, Tylka says finding the pest at any level means you likely need to address it.
Crop rotation and the use of SCN-resistant soybean varieties are cornerstones for managing SCN. Unfortunately, he adds, 95% of resistant varieties contain the same source of resistance – PI 88788 – and SCN is adapting.
“In those areas or fields where you find SCN, we would recommend planting corn and/or other management options such as seed treatments the following year,” he says.
Tylka recently discussed the issue of SCN on AgriTalk. You can listen to the discussion here:
