SUSTABILITY OF FIVE PREEMERGENCE HERBICIDES FOR CASSAVA(MANIHOT ESCULENTA CRANZ)

LO NYOK PIANG

SUMMARY

Two experiments were conducted to determine the suitability of five preemergence herbicides for cassava. The first experiment showed that alachlor [2-chloro-2', 6'-diethyl N-(methoxymethyl)- acetanilide], fluometuron [1, 1-dimethyl-3-(a, a, a-trifluro-m-toly) urea], and oryzalin (3. 5-dinitro-N⁴, N⁴-dipropylsulfanilamide) were safe to cassava at 1.5 kg/ha and produced a satisfactory weed control Applied at 1.5 kg/ha, diuron [3-(3, 4-dichlorophenyl)-1, 1-dimethylurea] induced some phototoxicityl tebuthiuron [N (5-(1, 1-dimethyl-ethyl)-1, 3, 4-thiadiazol-2-yl)-N, N-dimethylureal gave a long and excellent weed control but induced severe phytotoxicity. The second experiment confirmed that alachlor, fluometuron and oryzalin were selective and had a wide margin of safety to cassava. Diuron had been found to be partially selective and may not be safe if applied more than 1.5 kg/ha. However, it may be used in combination with alachlor at a reduced rate. It is concluded that suitable herbicides fbr cassava were alachlor, fluometuron and oryzalin

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