Effect of Soil Texture on the Damage Caused to Cotton by Reniform Nematodes

The reniform nematode (Rotylenchulus reniformis) is widely distributed in the Southeastern United States and can cause yield losses up to 40% in cotton.  The variability of soil textures in the Southeast not only affects soil moisture distribution, nutrient holding capacity, and yield potential; but also the fecundity  of reniform nematodes.  Reniform nematode populations are generally greater in soils with high than  low yield potentials, but the effects of the damage to the rooting structure are accentuated in the low yield potential soils. Traditionally, most cotton producers have been managing nematode problems simply based on nematode populations alone.  Most producers have obtained only one to a few nematode samples from a field and developed a management plan for that field based on the types and populations present. Current management strategies used to reduce losses due to nematode infestations include crop rotation and/or nematicide application (Overstreet and McGawley, 2000). Although this technique has worked reasonable well for managing nematode problems, in all likelihood this results in areas of a field that are either treated unnecessarily or not treated sufficiently.   Control  recommendations have traditionally been based on some “generic” threshold number that is applicable under certain conditions and are usually based on soil types where plants  will be damaged at these numbers (Overstreet et al 2008). In spite of this in-field variability of soil texture and nematode populations, farmers usually apply a uniform rate of Telone II across an entire field.  Blanket applications based on a constant rate often results in the application of Telone II to areas of a field that may not require treatment and as a result, lead to wasted inputs. Likewise, insufficient application may also allow damage levels that result in decreased yields.