Nematodes In The Crosshairs
March 3, 2009 The problem with nematode control is that there can be high populations with little damage in one section of a field, then low populations with severe damage in another.
“You have to understand that where nematodes are doesn’t mean you are getting damage, so what we are looking for is a response from the nematicide,” says Dr. Charles Overstreet, Extension nematologist and professor in the Department of Plant Pathology at Louisiana State University. His work has been funded through grants from Cotton Incorporated and EPA.
“Cotton Incorporated was a definite factor in the work we are doing,” Overstreet continues. “We are working on measuring nematode responses as you move across soil zones in fields. One of the ways we are looking at doing that is through soil conductivity.”
That requires a piece of equipment developed by Veris Technologies. A Veris machine is a pull-behind cart equipped with pairs of coulters with an electrode on each coulter. One electrode injects a known electrical current into the soil, while the other measures the drop in voltage as the current passes through the soil. Heavier soils conduct more current, while lighter soils conduct less. Once the amount of current that passes through the soil is measured, a detailed map is created showing variations in soil type across a field.
The Veris technology is so popular these days that it has become a verb: “We have to Veris that field.”
“The sandier the soils, the more likely you are to have root-knot nematodes, particularly,” Overstreet says. “That is also where we discovered that you are more likely to get damage. As the soil has more clay content, you might not limit the population of root-knot nematodes, but you certainly don’t see the damage you get in sandy soils.”
Overstreet adds that the same basic scenario can be applied to the reniform nematode, which tends to thrive in silt loams and heavier clay soils.
“What we do is get a picture from the Veris,” Overstreet says. “We break the field into zones – five to seven zones per field. We can then look into each individual zone to determine the yield responses.”
Dr. Ed Barnes with Cotton Incorporated adds, “There was some good progress in ’06 in finding ways to rapidly map root-knot nematode infestations. The approach has been tested and is holding up. We think this will be an additional good use of the technology.”
The Correlation
Maps created by yield monitors are overlaid with Veris maps to give a detailed report on what nematode damage occurred where. “Yield maps would show areas where damage is in the field,” Overstreet says. “Then, we look at the soil types and develop a relationship between soils and damage.”
That correlation leads to something you had to know was coming: Prescription application of nematicides.
“When you use a Veris map and a yield monitor map, you can see where you are getting responses and where you are not,”
And just as importantly, determining which zones do not. “Instead of the way we used to do business – treating the whole field with a nematicide – our goal is now is to only treat the parts of the field where the problems are,” says Overstreet.
Overstreet’s work has been with Telone, K-Pam, Vapam, Temik and Avicta Complete Pak.
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