Journal of Weed Science and Technology

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This study evaluated the effect of 23 herbicides used for paddy rice and paddy levees to control the growth of alligator weed (Alternanthera philoxeroides (Mart.) Griseb.). Stem fragments of the alligator weed were planted in pots in April, June, and August 2020. The herbicides were then applied during pre- and post-regeneration and vegetative growth stages of the weed. Some of these herbicides, including pyraclonil and florpyrauxifen-benzyl (Flo), were reported to effectively control alligator weed. We observed that when pyraclonil was applied during pre- and post-regeneration stages and when Flo was applied during post-regeneration and vegetative growth stages of the weed, they both reduced the dry weight of the weed. A regression analysis of the dry weights of the planted stem fragments and the regeneration plants treated with the paddy rice herbicides was performed for each herbicide, and it was found that the dry weight of the planted stem fragments was a variable factor of herbicidal activity, particularly under flooded conditions. However, Flo controlled the weed growth regardless of the dry weight of the planted stem fragments. Foliage-applied herbicides used for paddy levees were effective in managing both above- and below-ground parts though vegetative growth stage of the weed. Specifically, the application of dichlorophenyl dimethyl urea, glyphosate potassium salt, bispyribac-sodium (3%) and Flo (the use of which in paddy levees is illegal) at the vegetative growth stage of the weed completely killed both above- and below-ground parts of the weed.

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