Site-Specific Nematode Control
February 22, 2010 Controlling root-knot nematodes in cotton is difficult.
First, there are no rotational opportunities. Corn is often thought to be a non-host of the root-knot nematode, and that’s a dangerous misconception. Corn is a non-host to the reniform nematode.
“Corn and grain sorghum are both attacked by the root-knot nematode,” says Dr. Allen Wrather, with the University of Missouri’s Delta Center in Portageville. “There are some soybean varieties that have a little bit of resistance, but not much, so I don’t recommend that as a way to control them.”
The most commonly used nematicide types are used as on-seed treatments, in-furrow or as side-dressings.
“And there’s a fourth that has been available for many years, but is seldom used and that is because it’s expensive,” Wrather says. “It’s Telone and it’s by far the best product on the market. You have to use 3 gallons per acre and it costs about $13 per gallon, so the cost per acre is about $40, just for the chemical.”
Telone II is a soil fumigant from Dow AgroSciences.
And the second difficulty in controlling root-knot nematodes is that they are not evenly distributed across a field.
“Since root-knot nematodes are not uniform in a field, we think it’s logical to apply the product site specifically – just apply the product where the root-knot is present,” says Wrather. “If only 10% of a field is damaged, then it only makes sense to treat that 10%. That dramatically reduces the cost.”
Root-knot nematode research has shown that the pests thrive in sandier soils, and Veris EC technology is the most common way to create soil texture maps.
But Wrather believes a more accurate way to determine which areas of a field need treating is to use an old-school approach.
“We’ve tested several methods for detecting root-knot nematodes, and the method with the highest success is to examine the roots after the stalks have been shredded in the fall to determine where the roots have been galled,” he explains. “We’ve compared that with soil sampling and with Veris mapping. The Veris mapping system works very well, but not as well as examining the roots themselves.”
Taking a Hike
Using Wrather’s method, start in the corner of a field and walk down the row, taking a sample every 100 feet. When you’ve reached the end of the field, step off 100 feet across it, and go back the other way. Repeat until you’ve covered the field.
Wrather says to look at 5 to 10 plants at each stop, taking about 5 minutes to examine the plants at each site.
“That’s the time it takes to walk from one site to the next, dig 5 to 10 roots up, evaluate them for nematodes, then start walking to the next site,” he explains. “That sounds like a lot of samples and it’s four per acre. If you’re accustomed to grid sampling for nutrients, you take one per 2.5 acres. That’s fine for nutrient analysis but not for root-knot nematode analysis, because they can be in small areas ― sometimes as small as a half acre. You won’t find them unless you sample every 100 feet.”
If you choose to hire an consultant, Wrather says expect to pay on average $16 per acre for sampling and developing a map.
“Fortunately, we think the map will be useful for 2 years, and you may not have to do it but every 3 years,” he says. “But right now, we’re saying every two years, so that would cut your cost to $8 per acre.”
But a distinct advantage a Veris-created soil map has is that it will take an act of God to change the soil. Once the map is created, its useful life is infinite.
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Michael Roberts made 1,540 pounds per acre with a quality of 3 cents over the loan with PhytonGen’s PHY 375 WRF and site-specific applications of Telone.
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Dr. Allen Wrather
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