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Corn+Soybean Digest

The SCN Fight: Round 2

The SCN Coalition answered the bell for an all-out fight against this heavyweight soybean profit stealer last year. Now, it's Round 2.

The goal of the now 12-state coalition: kick some butt against soybean cyst nematode. That culprit causes more than $1 billion in losses in the U.S. each year.

The cry of the coalition: "Take the test. Beat the pest."

Taking the test means having soil samples tested to identify SCN infestations. It's the first step toward knocking out this costly opponent with crop rotation and resistant varieties.

Did the coalition kick some butt? It sure got a good start.

Consider these results: The Iowa State University (ISU) Plant Disease Clinic processed 4,335 soil samples for SCN in 1998 - a 250% increase over the 1997 number.

"The number of samples submitted in 1998 was more than the total number of samples processed at ISU from 1993 to '97," reports Greg Tylka, ISU extension nematologist.

The University of Minnesota reported 3,200 requests for SCN soil tests, 300% more than in 1997. The University of Missouri had 8,000 requests in '98, a 101% jump. Ohio State University reported a 993% hike in requests; Purdue University, a 400% increase.

Wisconsin, where soybean acreage is relatively small but growing fast, had 425 requests - a whopping 1,600% increase.

Remember, private lab testing adds to tests done by university labs. In Illinois, for example, all testing is done by private labs, many whose personnel were trained by the University of Illinois Extension Service. In 1998, these labs processed 11,331 soil tests.

The SCN Coalition added two new partner states - Kansas and North Dakota - this year. They joined the ground-breaking partnership of state soybean boards and land grant universities from 10 North Central states. Those states include: Illinois, Indiana, Iowa, Michigan, Minnesota, Missouri, Nebraska, Ohio, South Dakota and Wisconsin.

There was some good news in these test results. For example, in Iowa, no SCN eggs were detected in 48% of those samples. And 28% had low egg densities. Samples were tested from every Iowa county except seven.

Nevertheless, sampling often isn't intense enough to catch detectable populations in every field tested. Small hot spots could be missed entirely. And Tylka estimates that more than 70% of Iowa fields may be infested. Similar estimates come from scientists in other states where soybeans have been grown intensively for a lot of years.

There's no way now, nor in the near future, that this profit-stealing bugger can be wiped out. But, the good news is that we have enough management answers right now that it can be controlled well enough to avoid most yield losses. And if you catch it early, you never need to accept big losses.

"I feel very strongly that it's better, as they say, to nip the problem in the bud rather than wait until you're suffering losses up to 8 bu/acre or more and then try to do something about it," says Dale Edwards, University of Illinois extension nematologist.

Regrettably and astonishingly, after all the information that has been given out this past year and in years before, situations that can only be characterized as "lack of knowledge or denial" still exist in some quarters, and not just among growers, insists Edwards.

"Believe it or not, I had a call from a grower who had sent a sample to a private lab, and they told him not to grow soybeans again. Now that's something to tell a farmer in Illinois or elsewhere in the Midwest, isn't it?"

Greg Noel, a USDA-ARS nematologist at the University of Illinois, agrees.

"There are still people running around saying that you don't need to worry about SCN until you see stunted, yellow soybeans. And we know that's simply not true," says Noel. "I guess you can only call that ignorance. Fortunately, the work by the coalition is helping to minimize that ignorance factor, and it is increasing grower knowledge as to how serious this nematode problem really is."

SCN can rip yields 5, 10 and even 15 bu/acre on highly productive ground in the Midwest - while showing little or no above-ground symptoms. In fact, warns Noel, by the time you notice typical above-ground symptoms, you very well may have been taken to the tune of $50/acre - or more.

There's no disagreement among nematologists on the importance of soil sampling for SCN. Edwards, a long-time nematode fighter, puts it this way: "If I were a farmer, I would sample all of my fields. I'd probably start with problem fields first. But, as soon as feasible, I'd get through all my fields.

"My advice to growers," he adds, "is if you have some unexplained drop in yield, look for cyst nematodes as one of the possible problems."

Eddie Hoff, a Boonville, MO, grower with several years of experience fighting SCN, whole-heartedly seconds that advice.

"If a farmer hasn't tested for cyst nematodes, and has hit a yield lid he can't break through, the odds are great that he has nematodes or nematodes in combination with some other disease he's not on top of," says Hoff.

Sums up Tylka: "Fortunately, soil sampling for this pest is easy, effective and relatively inexpensive. Early detection of SCN infestations is an extremely important first step to effective, integrated management of this pest. If you need help to find out how to start soil sampling for nematodes, simply contact your county extension office."

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