Nematodes annually take 5 percent of the U.S. cotton crop, on average. Some fields lose as much as 25 percent to these invisible bandits.
John Mueller, Clemson university Extension nematologist, estimates annual losses of 1 million bales, nationwide.
Primary culprits are the reniform and root-knot nematode species, but others, including the Columbia Lance — mostly a South Carolina pest — add to the damage.
Varieties resistant to the root-knot have been available for several years but producers have relied primarily on rotation and chemistry to control reniform nematodes.
Growers may soon have another option, says Jason Woodward, PhytoGen cotton development specialist for the Mid-Atlantic.
Woodward, at a recent PhytoGen field day near Mayesville, S.C., discussed experimental varieties that show good resistance to reniform nematodes.
“We're looking at a new breeding trait,” Woodward says, “as a solution to reniform nematode problems in cotton. We’re dealing with a breeding trait very similar to what we've seen with our root-knot nematode resistance. We are evaluating this material internally to get a better understanding of how varieties that possess this trait perform in fields where reniform is a problem.”
Trials across the Cotton Belt evaluate in-season performance compared to susceptible varieties and also paying close attention to what occurs below ground nematode populations in the soil.
Woodward says currently trials are in a “proof of concept” status but he expects to have seed available to a few growers across the Belt in “a targeted approach in a number of locations in the Mid-Atlantic, the Southeast, the Mid-South and West Texas. We’re getting a good understanding of what to expect.”
He says in addition to managing nematodes, these experimental varieties show improved yield in fields with identified reniform nematode populations, in comparison with susceptible varieties.
“In preparation for launch, we're moving into our PhytoGen Horizon Network (PHN) growers testing program where we will get a limited amount of material out in 2020 and then ramp that up for a commercial launch in 2021.”
Those new releases will include resistance traits for both the reniform and root-knot nematode species, Woodward adds.
“Root-knot and reniform are the two most important nematodes throughout the Cotton Belt,” Woodward says. “We feel like the breeding traits we're looking at here provide a good opportunity to manage those two nematodes. We're going to have varieties with the two gene traits for root-knot resistance we've had in the past.
“In addition, new varieties will feature a new native breeding trait for reniform resistance.” New varieties also will include bacterial blight resistance, a standard for PhytoGen cottonseed.
Resistant varieties, he adds, will offer producers new options for a pest that often goes unnoticed. “Nematode losses often go unrecognized and they can be severe. It’s not uncommon to see areas in field hotspots go above the average; we've seen significant reductions of 25 percent across the board.”