AbstractA field study was conducted at Gurabo and Juana Díaz, Puerto Rico, to evaluate the use of plastic mulch and herbicide sequences as an alternative weed management for sweet potato [Ipomoea batatas (L.) Lam.]. Concurrently, efficacy of and tolerance to dimethenamid in sweet potato was assessed in the response of eight sweet potato lines to broadcast application of dimethenamid and clomazone herbicides. For the herbicide sequence, treatments were 1) plastic with paraquat at 0.56 kg ai/ha; 2) ametryn at 6 kg ai/ha with sethoxydim at 0.45 kg ai/ha; 3) clomazone at 1.12 kg ai/ha with sethoxydim at 0.45 kg ai/ha; 4) dimethenamid at 1.68 kg ai/ha with sethoxydim at 0.45 kg ai/ha; 5) clomazone at 1.12 kg ai/ha with clethodim at 0.11 kg ai/ha; and 6) clomazone at 1.12 kg ai/ha with clethodim at 0.22 kg ai/ha. Predominant weeds were junglerice (Echinochloa colona), purple nutsedge (Cyperus rotundus), spleen pigweed (Amaranthus dubius) and dayflower (Commelina diffusa). Herbicide treatment by location interaction was significant for yield. Yield was higher at Juana Díaz for all of the treatments except for that of plastic with paraquat. The use of dimethenamid followed by sethoxydim resulted in 9,614 kg/ha less sweet potato yield than with the use of clomazone followed by sethoxydim. At Gurabo, no significant difference was found among herbicide treatments for weed density and sweet potato yield. Neither crop injury nor phytotoxicity was observed when dimethenamid at 1.68 and 3.36 kg ai/ha was applied. Promising new lines of sweet potato tolerated clomazone, dimethenamid and clethodim.
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