Weed Control in the Tropics

Abstract

Weed control in the tropics requires mechanical labor plus systematic chemical treatment. A satisfactory contact spray includes: medium gravity highly aromatic oil, 30 lbs.; pentachlorophenol, 2 lbs.; Oromte wetting agent, 2 lbs.; and water, 95 gals. Two weed-killing oils are Shell #20 and Standard (of California) #2. In making the spray emulsion, the Oronite and pentachlorophenol are dissolved in the oil with gentle heat; the concentrate is emulsified in water. After mixing, gentle agitation keeps it stable. This emulsion kills all green vegetation, but not cane, coffee, pineapple, or banana plants if used only around the bases. It is a pre-emergence spray before planting and a general contact spray against all weeds when the shoots are a foot or more in height. This spray will not control all weeds. One lb. of 2,4-D can be added to the concentrate consisting of the 3 first items of the formula given above, and the emulsion spray will kill grasses, Commelina, coqui, bejucos, mor-ivivi (Mimosa pudica) and many other weeds. Coarse, vigorous grasses may also be controlled. Two pounds of pentachlorophenol are dissolved in 1 gal. of the aromatic oil descr. and this is mixed in 100 gal. of diesel fuel, waste crank-case oil, or any other light oil, and this will give excellent results if it covers the grass thoroughly and soaks down the crowns.