Submitted to: Organization of Nematologists of Tropical America
Publication Type: Abstract Only
Publication Acceptance Date: 9/2/1999
Publication Date: N/A
Technical Abstract: Crotalaria juncea (sunn hemp) and Hibiscus cannabinus (kenaf) are being tested as new fiber crops in the southern U.S.A., where the predominant crop grown is Upland cotton (Gossypium hirsutum). Five experiments were conducted during 1997-98 under growth chamber, microplot, and field conditions to examine the impact of sunn hemp and kenaf on Rotylenchulus reniformis and Meloidogyne incognita race 3, the two most damaging nematod pests of cotton in the U.S.A. Crop genotypes included sunn hemp cv. tropic sun, kenaf cv. Everglades 71, kenaf breeding lines SF459 and SF192, M. incognita-susceptible cotton cultivars Deltapine 16, Deltapine 50, and Deltapine 5409, and M. incognita-resistant lines Auburn 623 and Auburn 634. In the growth chamber and in two microplot experiments, each genotype was tested separately against M. incognita and R. reniformis whereas in the two field experiments, soil was infested naturally with a mixed population of the two nematodes. The results indicated that sunn hemp cv. Tropic Sun an probably other sunn hemp genotypes will greatly suppress both M. incognita and R. reniformis when used in rotation with cotton, whereas kenaf can support populations of R. reniformis as high as on cotton, and will support increases in M. incognita populations to levels that are devastating to cotton. Although sunn hemp suppressed both M. incognita and R. reniformis, it supported a high population of Pratylenchus spp. at one site from the soil surface down to 45 cm. Graduated soil samples taken in 15-cm increments to a depth of 135 cm indicated that the highest population density of R. reniformis on cotton or kenaf in two naturally infested fields occurred 100 cm deep. The population densities of R. reniformis measured on kenaf and cotton at this dept were 5-10 times those at 15 cm.