Efficacy of fumigant nematicides to control Hoplolaimus columbus on cotton

Four rates of methyl bromide (Mbr) (16.8, 33.6, 67,2, and 134.4 kg a.i./ha) and one rate of 1,3-dichloropropene (1,3-D) (28.1 liters a.i./ha) were evaluated over 2 years for control of Hoplolaimus columbus on cotton. All nematicide treatments were applied through a tarpless subsoiler-bedder prior to planting cotton, Gossypium hirsutum cv. Dehapine 90. Nematode population densities were monitored before and after treatment, at midseason, and at harvest, and yields were measured at maturity. Soil fertility variables (pH, P, K, Ca, Mg) were measured for each plot. Cotton yields were significantly increased by treatment with 1,3-D in 1988 and by all nematicidal treatments in 1989. Levels of nematode control varied from year to year among treatments. The responses of H. columbus numbers to rate of Mbr were best described by quadratic regression models. Levels of soil calcium and magnesium were significant factors in a multiple regression model relating a measure of control efficacy to rates of Mbr.