Use of 2,4-Dichlorophenoxyacetic Acid Herbicides on some Woody Tropical Plants

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Abstract
The herbicidal action of 2,4-D was studied on Aroma marabu (Dichrostachys nutans) and Guao (Comocladia den-tata), 2 perennial woody weeds of great importance in Cuba. Toxicity was detd. successively by leaf discoloration, defoliation, and failure to regenerate new shoots from the crown after 2 months. During this time controls grew vigorously and regenerated rapidly after cutting back. On Aroma, 2 sprayings 5 days apart with 2,4-D 0.2% as Na salt, or one spraying at 0.3% were about equally effective. Addition of 0.5% spreader (Carbowax 1500) increased the effectiveness of the Na salt, giving about 99% kill as judged after 2 months. 2,4-D ester caused quicker defoliation, but less complete killing of basal buds. Spraying in the shade was slightly less effective than in full sun. Spraying on the underside of the leaves did not increase effectiveness, although stomata there were more numerous than on the upper side. Direct observations of stomata show that they increase their opening after sunrise, close sharply after noon and partially reopen before sunset. On Guao, the 2,4-D ester was more effective than the free acid with carbowax, or the Na salt; a single spraying with the ester at 0.25% gave 75% kill. It is concluded that both these weeds can be largely eradicated by 2,4-D.