Evaluation of host-plant resistance and high residue rye for management of Meloidogyne incognita in cotton

The root-knot nematode Meloidogyne incognita (Mi) is the most important pathogen of cotton in the southeastern United States. Cotton cultivars with resistance to this nematode are commercially available; however, they have not been widely adopted by growers in fields infested with M. incognita. The objective of this study was to determine whether rotations of Mi-resistant (cv. PHY 487 WFR) and susceptible (cv. PHY 490 W3FE) cotton can be combined with high residue rye to provide a similar or better level of M. incognita suppression and cotton yield than continuous susceptible cotton with a nematicide (abamectin applied to the seed) or continuous resistant cotton. The experiment was a split-plot design with the cover-crop treatments of standard rye, high residue rye, and weedy fallow (main plots, eight replications each) and four management systems as the subplots. The management systems (subplots) were a resistant-susceptible (R-S) cotton rotation, a susceptible-resistant (S-R) rotation, continuous susceptible cotton plus nematicide, and continuous resistant cotton. The cover crop treatment had no effect on either mot galling in cotton or soil population densities of M. incognita J2 at plant, mid-season and harvest. Root galling from M incognita was greater in the continuous susceptible cotton with abamectin (S-S) and in the susceptible sequence in the rotation (R-S) than in the resistant sequence (S-R) and the R-R treatments. Populations of M. incognita J2 were lower in the spring following a resistant cultivar but increased by mid-season in the susceptible sequence of the rotation (R-S) to levels numerically above those observed for the susceptible cultivar with abamectin. Contrary to our expectations, the nematode suppression provided by the resistant cultivar had no carry over benefit to the susceptible cultivar in terms of reducing damage from M. incognita or improving yield. The cotton cultivar used was only moderately resistant to the nematode; perhaps a cultivar with a higher level of resistance may have had a more of a carry-over effect. Moreover, unlike a previous study, planting high residue rye in the winter did not reduce populations of M. incognita.