INFLUENCE OF TEMPERATURE AND ADJUVANTS ON THIDIAZURON ACTIVITY IN COTTON LEAVES

A laboratory study was conducted to determine the effects of two adjuv ants and temperatures at time of treatment on efficacy, absorption, an d translocation of thidiazuron defoliant on cotton. Five days after tr eatment at 30/21 C day/night temperatures, leaf drop was 17% with no a djuvant, 37% with addition of crop oil concentrate, 40% with ammonium sulfate, and 75% with two adjuvants combined. At 21/13 C day/night tem peratures, there was less than 10% leaf drop with all treatments. At 1 0 d after treatment, leaf drop was not different among treatments at t he high or low temperatures. Shoot regrowth at high and low temperatur e was reduced 55 to 60% with addition of both adjuvants and 44 to 50% with each adjuvant or with no adjuvant when compared to plants defolia ted by hand. Absorption of C-14-thidiazuron was not affected by variat ions in temperature during the time of treatment but was affected by a djuvants. With no adjuvants, absorption was 7 to 10%. With 1.25% by vo l crop oil concentrate, absorption was 33 to 46%. Addition of ammonium sulfate resulted in 18 to 19% absorption, and the combination of ammo nium sulfate and crop oil concentrate increased absorption to 65 to 68 %. There was no movement of radiolabel away from treated leaves as det ermined by autoradiographs of treated plants.