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Seed rot hits South Carolina cotton

The normal looking cotton bolls are full-sized and fully elongated with no damage on the outside. Inside the story is much different. Cotton fibers are immature. When the bolls crack, the lint is hard locked. And most baffling and striking, many of the seeds are dark and rotten.

This seed rot problem is costing South Carolina cotton growers as much as 10 to 15 percent of their potential yield, according to Clemson Extension Cotton Specialist Mike Jones. He also says the problem is beginning to surface in fields across the Southeast.

Jones and cotton growers across the state began noticing seed rot in apparently healthy bolls last year. Most of the rot problems were showing up in fields with lint yields of 500 to more than 800 pounds per acre. An intensive survey found seed rots in every county in the state, in irrigated and non-irrigated fields, early and late planting, and in all varieties, both transgenic and conventional, from all seed companies.

"This is still primarily a South Carolina problem, but there is enough concern in other states that we have put together a Beltwide group to evaluate varieties for susceptibility to seedrot," says Jones.

Speaking to cotton growers at the Third Annual Cropping Systems Field Day in Florence, S.C., Jones said North Carolina, Georgia, Alabama, Mississippi, Arkansas, Louisiana and Arizona are joining South Carolina in the project.

"A lot of the cotton varieties we are growing are genetically related. We thought that might be a key to finding the source of the seed rot problem," Jones says. "But so far this does not seem to be genetically related. The seed companies have helped us a lot in trying to evaluate this problem. We have still not found a cause."

Work in South Carolina this year also seems to say that whatever is causing the seed rot problems does not carry over in the soil. Jones planted cotton this year in a field near Furman where seed rot destroyed a high percentage of last year's cotton.

"That was the worst field in the state last year," he says. "This year we are finding hardly any seed rot in the same field, so it doesn't appear that whatever causes seed rot is carried over in the soil."

Some people speculated that Roundup Ready cotton sprayed with Roundup Ultra was more susceptible to seed rot than other varieties with other weed management systems. Jones' work this year lays that fear to rest. He says there is no greater incidence of seed rot in Roundup Ready or any other variety.

While seed rot is reducing yields, Jones says it should not reduce the quality of the cotton.

"When the seed rots, it cannot support development of cotton fibers. Those immature fibers could lower the quality of the cotton if they were mixed with fully mature cotton. But, most of the bolls with seed rot and hard locked cotton are knocked on the ground when the picker goes through. The picker can't pull the hard locked and immature fibers out of the bolls that remain on the plant," Jones says.

For now, Jones does not recommend that growers make any changes in variety selection or production practices. He urges growers to keep an eye open for signs of seed rot as they harvest this fall.

"Keep a record of where you find the problem, in which fields, with which varieties," Jones says. "We're going to continue to look for a cause and what we need to do to stop it. I'll have the results of this year's work in winter meetings."

Jones will also present the results of this year's seed rot work at the Southeast Cotton Conference in Raleigh on Tuesday, Jan. 23, 2001.

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