Submitted to: National Cotton Council Beltwide Cotton Conference
Publication Type: Proceedings
Publication Acceptance Date: 1/21/2001
Publication Date: N/A
Interpretive Summary: There are many kinds of microscopic worms called nematodes that feed on the roots of cotton and other crops, debilitating the plants and markedly decreasing yields. The direct losses to U.S. cotton farmers caused by nematodes were estimated by the National Cotton Council in 1999 to exceed $300,000,000. Although several different kinds of nematodes attack cotton, the reniform nematode and the cotton root-knot nematode are the most important in the U.S. A small number of cotton cultivars are resistant to the root-knot nematode but none are resistant to the reniform nematode. We evaluated the yield and nematode resistance of 40 commercially-available cultivars and new strains of cotton on a farm infested with the reniform nematode. None of them reduced nematode numbers in the soil enough to benefit the next year's crop but several did maintain high yields even though their roots were nematode infested. This information will help cotton farmers to select the appropriate variety to grow and will help seed companies develop new varieties.
Technical Abstract: Reniform nematodes have quickly become a major pest of cotton, causing severe losses across much of the U.S. cotton acreage. Presently there are no commercial cultivars available to growers with a significant level of resistance. This study was conducted in the 2000 growing season at the USDA-ARS North Farm reniform nematode nursery. The objective of the study was to determine the response of 40 commercially available cultivars and promising new strains of cotton in the presence of reniform nematodes. Twenty five of the better performing entries were reported in this paper. Average lint yield in the fumigated plots was 11.3% higher than for the reniform nematode infested plots. The top five producing entries in the reniform nematode infested plot averaged 46% more lint than Stoneville 474. A similar trend was observed in the fumigated plots. The experimental entry, NK 2723, produced the highest yield in the nematode infested plots and produced 15% more lint than the second highest yielding entry, MAR 280K-1-98. Final nematode population counts indicated that Stoneville 474 was the most susceptible of the 25 entries. Eleven entries had significantly lower counts than Stoneville 474. Fiber length in the reniform plots was longest for FiberMax 832 and TAMU 94L-25. Although no entry can be considered resistant, the results indicated that some cultivars and strains possess good tolerance to reniform nematodes.