Dr. Al Wrather, Professor, Plant Science Division, University of Missouri Delta Center, P.O. Box 160, Highway 61 South, Portageville, MO 63873, Phone (573) 379-5431, FAX (573) 379-5875, E-mail wratherj@missouri.edu.
Major Nematode Species: About 400,000 acres of cotton are planted annually in Missouri. All of the cotton is produced in seven Southeast Missouri counties: Butler, Dunklin, Mississippi, New Madrid, Pemiscot, Scott, and Stoddard. About 98% of the total is produced in Dunklin, New Madrid, and Pemiscot counties. Root-knot nematodes are a serious problem for Missouri cotton growers, especially in Dunklin, New Madrid, and Pemiscot.
Other Nematode Species: Nematode surveys were recently conducted in Missouri, and nine types of nematodes were found. Root-knot nematodes were the only ones found to cause yield loss in Missouri. Reniform nematodes were only found in 3% of the fields sampled, and the populations of these nematodes were much below threshold.
Estimates of Yield Loss to Nematodes in 2004: Scientists estimated that 2.0% of the 2004 Missouri cotton crop was lost to root-knot nematodes. This resulted in a loss of 13,800 bales valued at $3.97 million.
Average Yield Loss from 2000 through 2004 to Nematodes in Missouri: Scientists estimated that root-knot nematodes cut Missouri cotton yield an annual average of 0.85% from 2000 through 2004. This resulted in an average annual loss of 5900 bales valued at $1.69 million.
Activities to Consider during Late October: To determine if root-knot nematodes are a problem in a Missouri field, take soil samples for nematode analysis in the latter part of the growing season or just after harvest, from late-September through October. If these nematodes are present in a field, producers should take action to protect their cotton crop next year.
Recent Research Activities: Cotton growers continued to curse the root-knot nematode that annually costs them thousands of dollars in lost yields. Root-knot nematodes have reduced yields up to 25% in some southeast Missouri fields. Farmers have two weapons in their war against this pest; they may plant varieties tolerant to this nematode, nematode-resistant cotton varieties are not available, and they may use nematicides like Temik. Uniform application of Temik, in-furrow at planting in amounts suitable for nematode control, will protect cotton against early season damage by this pest. A problem with uniform application of nematicides is that these nematodes are not uniformly distributed in infested fields. Uniform applications of Temik in the past were often wasteful, because some areas were treated even though nematodes were not present.
Objective: The objective of our recent research was to determine the effects of site-specific nematicide applications. Nematicide applications were guided by a nematode-distribution map of the field. Recently, plots were established in a field near Leachville, AR that was infested with southern root-knot nematode, Meloidogyne incognita. The objective was to determine the correlation between fall root gall ratings on cotton in 12 locations in the field and yield differences during the next growing season between plots treated preplant with Telone and not treated at each location. These results showed that the difference in cotton yield between areas treated with Telone and not treated were well correlated with the gall ratings on cotton roots the previous fall. For example, yield for the Telone treated plots was 1192 lbs of seed cotton greater than the not treated plots in areas where the gall rating was severe the previous fall. However, there were no differences in yield for the treated and not treated plots in areas where the root gall rating indicated no root-knot nematodes present the previous fall. Fall gall ratings may be useful for directing site-specific application of Telone for management of Meloidogyne incognita.