Reniform in U.S. cotton: when, where, why, and some remedies.

The reniform nematode, Rotylenchulus reniformis, is an emerging problem in U.S. cotton. The impact of this nematode and the extent to which it has and will continue to spread across the U.S. cotton belt are controversial. Long-term changes in cotton production and unique biological attributes of R. reniformis are key factors. Expert opinion surveys indicate that R. reniformis has replaced the root-knot nematode (Meloidogyne incognita) as the major nematode of cotton in Mississippi, Louisiana, and Alabama. In neighboring states the incidence of heavily infested fields has increased during the past 10 years. Estimated annual loss to the U.S. cotton crop is $ 130 M. Crop rotation and nematicides can reduce losses. Introgression of genetic resistance from primitive accessions of other cotton species offers the most promising opportunity to effectively control this pathogen in the long term. Laboratories in several institutions are currently pursuing this goal, with the promise of resistant cultivars adapted to U.S. cotton production regions within three years.