Abstract
Bioefficacy studies of trifloxysulfuron-sodium, a new sulfonylurea herbicide, were conducted with and without surfactant and compared with glyphosate (Rodeo) and halosulfuron- methyl (Permit). In general, trifloxysulfuron-sodium was not effective without a surfactant, except the highest rate (31.5 g a.i./ha). Application of trifloxysulfuron-sodium with adjuvants (nonionic -X-77, organosilicone - L-77 or oil - MSO) significantly increased herbicide efficacy. Application of glyphosate at 500 g a.i./ha increased weed mortality significantly by providing 51%, 65%, 83%, and 88% control of yellow nutsedge (Cyperus esculentus L.), guineagrass (Panicum maximum Jacq.), redroot pigweed (Amaranthus retroflexus L.), and hairy Spanish needles (Bidens bipinnata L.), respectively. With the exception of guineagrass, increasing dosage of halosulfuron (8.75 to 35 g a.i./ha) did not influence yellow nutsedge, redroot pigweed, or Spanish needles. Trifloxysulfuron- sodium, even at 7.5 g a.i./ha, was comparable with the highest rates of glyphosate (500 g a.i./ha) or halosulfuron (35 g a.i./ha). Trifloxysulfuron-sodium at 30 g a.i./ha provided maximum control ( = 86%) of all the test weed species. In subsequent studies, application of trifloxysulfuron-sodium to three different citrus rootstocks resulted in significant phytotoxic effects to the primary stem in the form of necrotic leaves and further growth was stopped. However, upon pruning the necrotic tissue, lateral growth arose from the trimmed point followed by normal rootstock growth.
