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.