Impact of Cotton Production Systems on Management of Hoplolaimus columbus.

The effectiveness of selected cultural practices in managing the Columbia lance nematode, Hoplolaimus columbus, on cotton was evaluated in experiments in growers' infested fields. The effects of planting date, cotton cultivar, treatment with the growth regulator mepiquat chloride, and destruction of cotton-root systems after harvest on cotton-lint yield and population densities of H. columbus were studied. The yield of cotton cultivar Deltapine 50 was negatively related (P = 0.054) to initial population density of H. columbus whereas the yield of Deltapine 90 was not affected by preplant density of this nematode, indicating tolerance in Deltapine 90. Reproduction of this nematode did not differ on the two cultivars. Planting date and treatment with the growth regulator mepiquat chloride did not influence cotton yield in a consistent manner. Application of mepiquat chloride suppressed (P </= 0.05) numbers of Columbia lance nematode, although there was an interaction (P </= 0.05) with cultivar and year. Early vs. late destruction of cotton-root systems did not impact population densities of this nematode either year, and had no impact on the subsequent cotton crop. The nematicide fenamiphos increased (P </= 0.03) cotton yield when H. columbus numbers exceeded the damage threshold.