Population dynamics of Meloidogyne incognita, M-arenaria, and other nematodes and crop yields in rotations of cotton, peanut, and wheat under minimumtillage

Wheat, cotton, and peanut were arranged in three cropping sequences to dete rmine the effects of fenamiphos (6.7 kg a.i./ha) and cropping sequence on n ematode population densities and crop yields under conservation tillage and irrigation for 6 years. The cropping sequences included a wheat winter cov er crop each year and summer crops of cotton every year, peanut every year, or cotton rotated every other year with peanut. The population densities o f Meloidogyne spp. and Helicotylenchus dihystera were determined monthly du ring the experiment. Numbers of M. incognita increased on cotton and decrea sed on peanut, whereas M. arenaria increased on peanut, and decreased on co tton; both nematode species remained in moderate to high numbers in plots o f wheat. Root damage was more severe on cotton than peanut and was not affe cted by fenamiphos treatment. The H. dihystera population densities were hi ghest in plots with cotton every summer, intermediate in the cotton-peanut rotation, and lowest in plots with peanut every summer. Over all years and cropping sequences, yield increases in fenamiphos treatment over untreated control were 9% for wheat, 8% for cotton, and 0% for peanut. Peanut yields following cotton were generally higher than yields following peanut. These results show that nematode problems may be manageable in cotton and peanut production under conservation tillage and irrigation in the southeastern Un ited States.