The Influence of Various Additives on Absorption of Thidiazuron and Dimethipin

Gene D. Wills and Charles E. Snipes


 
ABSTRACT

Previous studies with thidiazuron (Droppr) have shown that the addition of 1.25% v/v crop-oil-concentrate (COC) plus 1 lb/A ammonium sulfate to the treatment mixture can double the percent of cotton defoliation at 5 days after treatment over that with the addition of COC alone. However, at 14 days after treatment, there was no difference in the percent defoliation between the different additive combinations. Further studies using 14C-radiolabeled Dropp showed that the addition of COC plus ammonium sulfate significantly increased the initial absorption of 14C-Dropp into cotton leaves over that with the addition of COC alone.

This study was conducted to determine the effect of other additives on the absorption of both Dropp and dimethipin (Harvader) into cotton leaves. 14C-radiolabeled Harvade with the specific activity of 65 mCi/mg was applied to a single leaf in the amount of 0.2 mCi in 10 ml of water in combination with either 1.25% v/v COC or 2% v/v HM-8802A (from Helena Chemical Co.), 2% v/v MYX-1220 or 2% v/v MYX-6121 (from Mycogen Corp.) or the combination of 1.25% COC plus 1 lb/A ethephon (Prep). 14C-radiolabeled Dropp with the specific activity of 15 mCi/mg was applied to a single leaf in the amount of 0.1 mCi in 10 ml of water in combination with each of the first four adjuvants as stated above plus 0.25% v/v LI-700 (from Loveland Industries, Inc.).

Treatments with each of these defoliants were conducted inside environmentally controlled growth chambers with photoperiods of 10-h night and 14-h day. Treatments were conducted simultaneously at cool 55o/70oF and warm 70o/85oF night and day temperatures for 24 hours with Dropp and 48 hours with Harvade.

Absorption of 14C-Harvade was 84 to 91% of that applied under all conditions of this study. With the addition of COC, 14C absorption was lower (84-85%) at the cooler night/day temperature. There was no significant difference in 14C absorption (88 to 91%) among the other additives at either cool or warm temperature.

Absorption of 14C-Dropp was 21 to 42% of that applied. The greater absorption occurred at the higher temperature with HM-8802A (42%) and LI-700 (36%) and at both warm and cool temperatures with the COC (35 to 37%). The lowest absorption was at the cooler temperatures with MYX-1220 and LI-700 (23%) and at both warm and cool temperatures with MYX-6121 (21 to 23%).



Reprinted from Proceedings of the 1994 Beltwide Cotton Conferences pg. 1327
©National Cotton Council, Memphis TN

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Document last modified Sunday, Dec 6 1998