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Black rot, sclerontinia

Peanut farmers hit with the double-whammy disease tandem of cylindrocladium black rot (CBR) and sclerotinia could get help soon from a new variety showing resistance to both.

Researchers say North Carolina's newly released Perry variety has good CBR resistance and also some resistance to sclerotinia. Thatís better disease fighting ability than any other peanut variety available in the region. Until now, farmers could plant peanut varieties with reasonably good CBR resistance. Sclerotinia resistance was tougher to breed into the plant, however, and breeders could not successfully mix it with CBR resistance until the breakthrough with Perry.

“We had a problem getting resistance to more than one type in a peanut,” says Jack Bailey, North Carolina Extension plant pathologist. “Now Perry will provide some resistance to two of our major diseases. Farmers don't have to go backwards on CBR resistance to get sclerotinia resistance. It's a really important development for our farmers.”

A Virginia type peanut, Perry recorded high yields under test conditions. “It has been a good high yielding variety even without the diseases being present,” says David Jordan, North Carolina Extension peanut specialist.

Plant breeder Tom Isleib, building on the work of his predecessor Johnny Wynne, should be commended for developing Perry, Bailey says. “This comes out of a traditional breeding program and is not a biotech variety, though biotechnology techniques are being used in research at NCSU. Last season there were only 3,000 acres of Foundation seed of Perry. This year everyone should have to opportunity at least to see it.”

“Peanut resistance to diseases fits perfectly with farmers' situation, where they're trying to reduce input costs. To the degree that you can control diseases with resistance and rotation, that's the way to do it.æ

Stopping sclerotinia at all should excite many peanut farmers. “It”s a very nasty disease, a big deal, the biggest yield reducer we have,” Bailey says.

Until a few years ago, CBR held that dubious distinction. Then varietal resistance curbed CBR while sclerotinia grew worse. Once introduced into a field, it spreads easily.

“Sclerotinia is in all the state's peanut counties. Even with the resistance in Perry, some spraying for sclerotinia will still be necessary,” Jordan says.

Syngenta's Omega 500, with a special Section 18 label last season, helped some farmers reduce sclerotinia problems. The product could be fully labelled for use this season, but an application for a new Section 18 permit has been submitted, anyway.

“It works, but you have to use it properly,” Bailey says. “You have to understand the history of the field and what part of the field has a sclerotinia problem. You need to focus on early application, when the vines are nearly touching. You should do it when the weather conditions are favorable for developing sclerotinia, which is rainy and relatively cool.”

“Outbreaks tend to follow rain,” Jordan says. “The most accurate assessment of the weather is done with the sclerotinia advisory program. The big question at farmer meetings this winter was how they could get some Perry to plant on their farm.”

This season, however, only certified seed growers will get to plant the variety. It will be in general release in 2002.

“It'll take on a high percentage of our acreage, even if it does stumble a little due to some unforeseen problem that didn't come up in the tests. Farmers are excited about it and want it now,” Jordan says.

North Carolina State University researchers are also testing biological controls for sclerotinia. The most intriguing is another fungus discovered in Germany, registered as Contans, which attacks the sclerotinia fungus.

“We don't now recommend using Contans because, even though it is registered, we donít know how effective it is,” Bailey says. “We know it will attack sclerotinia. The question is if it's effective enough to be efficient. If it can do that, it's a real breakthrough. Then the farmer could change the soil ecology by introducing a friendly fungus to destroy another one.”

These below-the-soil-surface battles are common with naturally occurring organisms in fields.

“There are lots of attacks in the soil that we never see,” Bailey says. “There's a war going on down there. Everybody is steak dinner for somebody. Contans will be applied in tests in fields with known sclerotinia problems this season. We're going to see if it's really economically viable. When those results come in, we'll know a lot more about it.”

There's a new coordinated approach to stopping the spread of CBR this year. Pathologists now believe CBR is transmitted on seed, so shellers are implementing special programs on certified seed production fields to avoid the disease. Seed treatment can reduce by half the transmission from infested or “speckled” seed.

North Carolina State University specialists working with the seed industry have developed a plan including specifications that certified seed production is to be only in fields with low levels of CBR and fields with a history of CBR be fumigated prior to planting. At season's end, they'll be inspected. and seed from fields with greater than 5percent CBR disease infestation must be rejected.

“This should have a major impact on the spread of CBR, Jordan says. “It's a real issue and everybody agrees it's a real issue and we're going to do what we have to do to keep it from becoming an even more major problem.”

“This new certification program is a perfect example of how the university and industry works together,” Bailey says. “While it is inconvenient to put new policies in place, this sort of active screening is part of the necessary effort required to keep the quality of the seed supply high. In fact, one of the hallmarks of American agriculture is the rapid adoption of new research findings. It is our competitive advantage over our competition overseas.”

All told, it's an encouraging scenario for peanut farmers plagued with disease problems.”New varieties and high quality control make our peanut growers the best in the world,” Bailey says.

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