EFFECT OF TCA ALONE AND IN COMBINATION WITH 2,4-D ON WHEAT: CROP TOLERANCE AND TCA RESIDUES IN WHEAT

Abstract

The tolerance of spring wheat (Triticum aestivum L.) to TCA (trichloroacetic acid) applied alone and tank-mixed with 2,4-D [(2,4-dichlorophenoxy)acetic acid] was assessed in weed-free field plots for three seasons. Under weed-free conditions, the interaction of 2,4-D with TCA was not significant and thus the tolerance of wheat to TCA was not increased by the addition of 2,4-D. Plant height and kernel weight decreased with increasing rates of TCA. The number of culms headed increased with increasing rates of TCA; however, grain yield, as well as germination and plant dry weight were not affected by any TCA treatment. Residues of 2,4-D were not detected in the grain and straw at the limit of detection of the analytical method (0.05 ppm). In contrast, 1.0 and 0.79 ppm of TCA remained in the grain and straw, respectively, for the 1.12 kg/ha rate. Milling substantially reduced TCA residues originally in the treated grain, such that residues in the bran and flour were 0.25 and 0.11 ppm, respectively, for the 1.12 kg/ha rate. After baking the flour into bread, TCA residues were not detected at the limit of detection of the analytical method (0.05 ppm).Key words: TCA, 2,4-D, wheat, crop tolerance, residues