Dr. Michael McClure, Department of Plant Pathology, 204 Forbes Building, University of Arizona, Tucson, AZ 85721, Phone (520) 621-7161, FAX (520) 621-9290, email: mcclure@ag.arizona.edu
Major Nematode Species: Two nematode species that inflict significant injury to Arizona’s cotton crop are root-knot and lesion nematodes. Root-knot nematodes account for more damage than lesion nematodes. In a typical year, more than 250,000 acres in the state’s eight county producing area are planted in upland and Pima cotton. In 2003, approximately 217,500 acres of cotton were planted. Cotton producing counties are: Cochise, Graham, Greenlee, La Paz, Maricopa, Pima, Pinal, and Yuma. In 1995, survey activities identified heavy infestations of root-knot nematodes in Maricopa, Pinal, and Cochise counties ... and medium densities of root-knot nematodes in Greenlee, Cochise, and Pima counties.
Other Nematode Species: Three other nematode species have been reported on cotton in Arizona: stubby root, stunt, and stem nematodes. In 1992, a survey of 113 townships in six counties reported that 32% of field soil samples were infested with stubby root, stunt, and stem nematodes. Reniform and Columbia Lance nematodes have not been detected in any samples from the cotton-producing counties.
Seven-year Average Yield Loss Estimate from 1997 through 2003: Annual average of 5% of the crop was lost to nematode damage ... 35,310 bales ... valued at $10,289,250.
2005 Activities to Consider in Latter Part of Growing Season: Because of substantial yield losses recently, growers are advised against complacency. Nematode management programs point the way to reducing the damage caused by nematodes in the state. Relying on soil samples to identify nematode species and densities ... plus judicious applications of cultural and chemical controls are critical to future cotton production in Arizona. The best time for nematode soil sampling is July and August, during the peak of the growing season. Later sampling is difficult, because irrigation often has been terminated, and the soil is too dry for good results. Early spring sampling, while possible, does not allow enough time for host-range testing of root-knot populations.