The crop nemesis southern root knot nematode (RKN), Meloidogyne incognita, may have met its match in Arizona crop fields thanks to improved targeted applications of soil fumigants in various soil textures delivered through precision agriculture technology.

Field trials conducted from 2006 to 2010 tabulated information gathered by global positioning systems and variable rate technology, including the electrical conductivity-based Veris 3100 and EM38 sensors for on-the-go soil mapping, plus harvest yield mapping data.

This technology illustrates that nematicide applications can be applied sparingly in some cases while maintaining good nematode control and trimming chemical costs.

The grower cooperator field trials included six studies with the nematicide Telone II applied at pre-plant in cotton and corn in central and southwestern Arizona conducted by University of Arizona (UA) researchers Randy Norton, Tim Hatch, Mike McClure, and Pedro Andrade.

Norton, UA regional extension cotton specialist based in Safford, shared the findings during the 71st annual Cotton Disease Council meeting at the 2011 Beltwide Cotton Conferences in Atlanta, Ga., in January.

Norton labeled the RKN as the No. 1 nematode species threat in Arizona. The microscopic roundworm damages crops by attacking the young tap and secondary roots which stimulates the production of galls. Galls interfere with the ability of the roots to absorb water and nutrients, and allow other disease-producing organisms to enter the plant.

Arizona hotspots for RKNs include the Coolidge, Casa Grande, Florence, and Buckeye areas in central Arizona and the Bonita area in the Sulphur Springs Valley in southeastern Arizona.

In cotton, the RKN is responsible for a 5 percent lint yield reduction on average across the Cotton Belt, Norton says. Five gallons is the standard Telone II application rate in Arizona to maintain cotton yields in RKN-infected fields.

“The 5 gallon Telone II rate results in tremendous increases in cotton yield per acre,” said Norton, a cotton agronomist. “Heavy RTK infestations without Telone II can result in nearly complete crop loss in highly infested areas.”

Soil texture is directly related to Telone II efficacy. Many Arizona crop fields contain stream and river deposited alluvial soils. A 70-acre field, says Norton, can have five to six soil classifications with high soil texture variability which impact nematode numbers and distribution. The tests reveal that soils dominated by sand have higher RKN numbers. Clay loam-based soil has a low RKN population.

The field trial locations were selected on baseline nematode levels and growers’ experiences. The Veris mapping survey divided the fields into four management zones; Zone 1 with the most sand to Zone 4 with the least sand. A prescription was developed based upon the zones. Zones 1 and 2 were treated with Telone II. Zones 3 and 4 were untreated.

Each trial layout included verification strips (treated and untreated) placed across the field to cross all management zones. Yield data was obtained from a monitor at harvest. Full-length strips across all zones were evaluated along with the yield response within each zone (Telone treated and untreated).

“Observational data suggests that the entire field does not always require a nematicide application,” Norton said. “The ability to target and apply a nematicide to specific areas of a field predicted to have a high potential for crop damage while avoiding application on areas of the field with a low potential for crop damage allows the grower to greatly enhance the efficiency of nematode control thereby improving profitability and reducing the amount of nematicide released into the environment.”