Meta-Analysis of the Field Efficacy of Seed- and Soil-Applied Nematicides on and Across the U.S. Cotton Belt.

Meta-analysis was used to compare yield protection and nematode suppression provided by two seed-applied and two soil-applied nematicides against and on cotton across 3 years and several trial locations in the U.S. Cotton Belt. Nematicides consisted of thiodicarb- and fluopyram-treated seed, aldicarb and fluopyram applied in furrow, and combinations of the seed treatments and soil-applied fluopyram. The nematicides had no effect on nematode reproduction or root infection but had a significant impact on seed cotton yield response ([Formula: see text]), with an average increase of 176 and 197 kg/ha relative to the nontreated control in and infested fields, respectively. However, because of significant variation in yield protection and nematode suppression by nematicides, five or six moderator variables (cultivar resistance [ only], nematode infestation level, nematicide treatment, application method, trial location, and growing season) were used depending on nematode species. In -infested fields, greater yield protection was observed with nematicides applied in furrow and with seed-applied + in-furrow than with solo seed-applied nematicide applications. Most notable of these in-furrow nematicides were aldicarb and fluopyram (>131 g/ha) with or without a seed-applied nematicide compared with thiodicarb. In -infested fields, moderator variables provided no further explanation of the variation in yield response produced by nematicides. Furthermore, moderator variables provided little explanation of the variation in nematode suppression by nematicides in and -infested fields. The limited explanation by the moderator variables on the field efficacy of nematicides in and -infested fields demonstrates the difficulty of managing these pathogens with nonfumigant nematicides across the U.S. Cotton Belt.