Greener Journal of Plant Breeding and Crop Science Vol. 1 (1), pp. 001-007, September 2013.
ISSN: 2354-2292 © 2013 Greener Journals
Manuscript Number: 031913532
Effect of Pethoxamid (TKC-94) Rate and Application Time on Weed Control and Phytotoxicity in Flue-cured Tobacco
University of Zimbabwe, Crop Science Department, P. O. Box MP 176 Mt Pleasant, Harare, Zimbabwe.
Due to the risk of weed resistance to herbicide control, there is continuous need for new chemicals to be tested for control of weeds. Such work is of major importance as herbicides form a vital line of defence against weeds which would otherwise cause yield loses of even up to 100%. In this work, the herbicide pethoxamid (TKC-94) was evaluated to establish the time and rate of application that would give efficacious weed control without causing phytotoxicity. In the first year, the herbicide was included in a simple screening trial comprising twelve herbicides arranged in a randomised complete block design. After it had stood out it was selected for further development. In the second year, in a split plot design with four blocks and six treatments, it was applied as TKC-94 at 1.88 kg a.i /ha applied just after holing out (a.h.o.) and TKC-94 at 1.88 kg a.i. /ha applied immediately after planting (i.a.p.). Three controls, Dual 960 ec (Generic, a.i. s-metolachlor) at 2.2 kg a.i. /ha i.a.p and Dual Magnum (original formulation, a.i. s-metolachlor) at 2.2 kg a.i. /ha i.a.p as checks and an untreated control were included. This trial showed that applied a.h.o., TKC-94 was phytotoxic, stunted Tobacco and reduced yield and weed efficacy while the i.a.p. was ideal and showed no phytotoxicity and had good weed efficacy. In the third year, the i.a.p. time of application was tested in a similar design but now, more rates of TKC-94 were tested. The rates were, TKC-94 at 0.0 kg a.i. /ha i.a.p, TKC-94 at 1.88 kg a.i. /ha i.a.p., TKC-94 at 2.82 kg a.i. /ha i.a.p., and TKC-94 at 3.76 kg a.i. /ha i.a.p. Dual Magnum at 2.2 kg a.i. /ha i.a.p was included as a check. This work confirmed the potential of the herbicide as a broad spectrum material and showed that the best rate that would ensure broad spectrum control was 2.82 kg a.i. /ha. Further research could look at application of this material in irrigation water in order to cater for those farmers with centre pivots. In addition, the early post emergence control of weeds may also need to be researched in order to give the farmer more flexibility in using this herbicide.
Keywords: Pethoxamid, flue-cured, TKC-94, tobacco, s- metolachlor.