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Cotton producer wins a battle with root-knot nematode

CRUGER, Miss. -- When cotton producer Buck Harris found high levels of root-knot nematodes in several hundred acres of sandy loam ground in the fall of 2001, his first reaction was that he’d have to quit growing cotton on the fields.

Two years later, he harvested 3.2 bales per acre from those very same fields, and cotton was back in the crop mix again.

The solution? A root-knot nematode-tolerant cotton variety, along with excellent planting and growing conditions in 2003.

The problem with the field began in the late 1990s. Harris’ son, Steve, who was farming the ground at the time, noticed that yields inexplicably began to decline from 1,000-1,100 pounds to 750-800 pounds. “At first, we thought it was due to (a problem with transgenics).”

Eventually, Steve decided to get out of farming and took a job with a local co-op. Harris stepped in and decided to have the field checked for nematodes in the fall of 2001. To his surprise, soil samples revealed that root-knot nematodes were at three times the threshold level.

Harris felt as though he had no other option but to put the field in a root-knot-tolerant soybean variety, Pioneer 9594. The variety yielded well in 2002, over 50 bushels an acre, but did not have a significant impact on nematode numbers that fall.

Harris, who this year will farm about 2,200 acres of cotton, was in a quandary on what to do, until he heard about a cotton variety tolerant to the fusarium and root-knot nematode complex. Harris planted 500 acres in the variety and later noted, “It was one of the best decisions I’ve ever made.”

After harvesting soybeans on the fields in 2002, Harris ran a hipper in the fields. Harris, who farms with his son, Mark, missed most of the rainy, spring weather that hit the north Delta in 2003. In fact, “we had to run a pivot to get some cotton up last year.”

Harris planted the root-knot-tolerant variety, ST 5599 BR, at 10 pounds of seed to the acre on April 25, applying Cotoran, Staple and Dual at the time of planting. “I’m old enough and been around long enough to know it can rain for 10 days. It scares me to have just Roundup out there without any protection at all,” Harris said.

He also applied Temik at 4 pounds per acre. A side benefit of the in-furrow insecticide was some degree of control for nematodes. Harris made one pyrethroid application for cotton bollworms. “Early in the season, I made two shots of Centric for plant bugs.”

Harris tries to limit his Roundup application to one shot. “If I do see the need for a second shot, I will make it. If I see some morningglories coming through, I’ll go in with a post application of Caparol and MSMA. I’ll layby with Diuron. This year, I may put out some Caparol and Diuron.”

Harris put out about 16 ounces of Pix on his ST 5599 BR.

All of Harris’ cotton ground is irrigated by furrow and center pivots. The ST 5599 BR field was irrigated three times in 2003, according to Harris. “I irrigate a little more than the average person, and I’m usually a little quick to pull the trigger. But over my 35 years, I’ve seen that it’s best to not let cotton stress.”

Harris goes with a two-step defoliation, Dropp and Prep, followed by Prep and Def. He harvested the crop in mid-September. “About 80 percent of the ST 5599 was picked only one time.

In 2003, yields were above 3 bales per acre across all Harris’ cotton acres, which included ST 5599 BR, DP 555 BG/RR and ST 4892 BR. “It was a tremendous crop. All my flat land planted to ST 5599 BR was 3.2 bales per acre. It was the best I’ve ever made on that land.”

DP 555 BG/RR yields were a little over 3 bales per acre. ST 4892 BR averaged about 2.6 bales per acre, but the variety was planted on heavier ground. “It is an earlier variety and I wanted to get it out before any rains.”

Of course, favorable weather at planting and during the season had a lot to do with Harris’ yields across the farm. “But if I had not had the ST 5599 BR, I would not have seen that large a crop. The root-knot numbers were so tremendous.”

This year, Harris will plant 350 acres of DP 555 BG/RR, 500 acres of ST 4892 R and 1,350 acres in ST 5599 BR. “I decided to plant enough corn, about 500 acres, to fill up my grain tanks, about 75,000 bushels. I’ll plant 1,000 acres of soybeans this year. I’m still banking that we’ll get the price right in cotton.”

Yes, he’ll be planting the root-knot resistant variety on fields that don’t have a problem with the pest, noting, “With those kind of yields, I’m going to gamble a little bit more and go with it.”

Limited research on ST 5599 BR’s level of root-knot tolerance is encouraging, according to Gary Lawrence, entomologist and plant pathologist at Mississippi State University.

Lawrence inoculated varieties planted in pots with a known number of either root-knot or reniform nematodes. In the case of root-knot nematodes, “We let the plant grow for 45 days, which is the maximum reproduction for one generation, then counted the nematodes again. We divided the final population by the inoculated number to arrive at a reproduction factor (RF).

“The RF for root-knot nematode was 1.3 (for ST 5599 BR), which is extremely good for root-knot. Other plants inoculated with reniform nematodes had a RF of 139.”

Harris is concerned about the high numbers of nematodes that have invaded his fields. He has both reniform and root-knot types, including some fields with both. That means sampling and understanding rotational partners is crucial to keeping them under control.

“It is about as important to take samples for nematodes as it is to soil sample for fertility,” Harris said. “It doesn’t do any good to get your foundation down there and have this type of problem knocking you down.”


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