Growth responses of cotton to aldicarb and temperature

Aldicarb, 2-methyl-2-(methylthio)propionaldehyde O-(methylcarbamoyl)oxime, is a systemic insecticide used extensively for early season insect control in cotton (Gossypium hirsutum L.). The indirect effect of aldicarb on cotton due to insect control is well documented; however, much less is known regarding its direct effect on cotton growth and development. The purpose of this research was to test the hypothesis that aldicarb in the absence of insects imposes a direct effect on cotton growth and that aldicarb effectiveness on growth depends on temperature. Cotton plants (cv. Deltapine-50 and DES-119) were grown in outdoor sunlit plant growth chambers under five day/night temperatures (20/12, 25/17, 30/22, 35/27, and 40/32 °C). In one study, aldicarb at 0.56 kg ha -1 was applied to soil at sowing. In a second study, aldicarb was first applied at a rate of 0.84 kg ha-~ to soil at sowing and applied again at a rate of 2.24 kg ha~ at the stage of flower bud initiation as a side-dressing. Aldicarb increased early season vegetative growth of cotton plants grown at 25/17, 30/22, and 35/27 °C, but not for plants grown at 20/12 and 40/32 °C. Aldicarb also promoted the early formation of cotton flower buds at the five temperature regimes and increased the number of flowers at 30/22 °C. The treated plants had more growing roots, greater root length densities in the 61-80 cm soil depth, and higher root/shoot ratios than control plants at all temperatures. Our results showed that aldicarb promoted cotton earliness by enhancing growth rates and promoting the roots to grow deeper into soil. The responses of cotton to aldicarb depended on temperature, with a greater effect occurring at near optimum temperatures for cotton growth. © 1997 Elsevier Science B.V.