Summary of nematode survey activity in Texas.

Dr. Terry A. Wheeler, Texas Agricultural Experiment Station, Route 3, Box 219, Lubbock, TX 79401-9757, Phone (806) 746-6101, FAX (806) 746-6528
email: ta-wheeler@tamu.edu

Major Nematode Species: Many different species of nematodes have been identified in the five distinct cotton growing regions in Texas. The most predominant are root-knot and reniform nematodes. Texas produces about 35% of all the cotton in the U.S. The state’s growing regions are geographically diverse and culturally unique from one another. On the High Plains of West Texas, cotton is produced under semi-arid conditions with limited irrigation. In central Texas, cotton is grown on the Rolling Plains. More conventional cotton growing conditions are in the southern and eastern portions of the state -- the Lower Rio Grande Valle, the Coastal Plains, and the Brazos River Valley. Historical data indicate that root-knot nematodes infest 40% of the fields on the High Plains. Reniform nematodes may also contribute significantly to the state’s yield loss. In 1995 surveys, heavy infestations of reniform nematodes were reported in nine counties -- Cameron, Hidalgo, Willacy, Wharton, Fort Bend, Burleson, Brazos, and Robertson. Approximately 25% of the 127 major cotton producing counties in the state have been surveyed for nematode population distributions and densities.

Other Nematode Species: Howard and Martin counties in the extreme of the Southern High Plains, and Mitchell, Nolan, and Runnels counties in the Southern Low plains were surveyed in 1992 for nematodes. Low density distributions of lesion and stunt nematodes were evident in these five counties.

1998 Yield Loss Estimate Valued at $390/Bale: 3% of the cotton crop was lost to nematode damage ... 101,010 bales ... valued at $39,390,900. Crop summary statistics for 1998 (NASS, USDA) show that 5,650,000 acres were planted, but only 3,300,00 were harvested. The severe drought caused this significant reduction in acres harvested. The yield in 1,000-lb. bales harvested in 1998, was 3,500,000.

Seven-year Average Yield Loss Estimate from 1992 through 1998: Annual average of 3.7% of the crop was lost to nematode damage ... 193,028 bales ... valued at $72,849,280.

1999 Activities to Consider in Latter Part of Growing Season: The best time to take samples for root-knot nematodes in Texas is two months before ... to six weeks after harvest. Researchers say this is the time when nematodes will be at their highest levels. Many Texas growers keep nematode populations below economic thresholds by combining chemical and cultural controls. Rotation with a non-host, or poor host like peanut or sorghum, is an effective control measure. Chemical nematicides are widely favored for effective short term control. The purpose for using nematicides is to provide a zone of protected soil in which cotton roots can develop for the critical first four to six weeks.

1998 Research Activities: Seven tests were conducted in the Texas High Plains to evaluate Temik 15G for the control of root-knot nematodes. One trial was done in each of five locations -- Brownfield, Lamesa, Ropesville, Seagraves, and Sundown. Two trials were done in Lubbock. 

For details of test results, contact Jennifer Gimpert.