Suitable Adjuvant to Maximize Trifloxysulfuron Efficacy and Early Assessment of Herbicide Efficacy Using Chlorophyll Fluorescence

Trifloxysulfuron 2.5, 5, and 10 g ai/ha mixed with non-ionic (0.25 % Induce and X-77), organosilicone (0.1 % Kinetic and Silwet L-77), and crop oil concentrate (1 % Agridex and Meth-N-Oil) adjuvants was evaluated for efficacy, surface tension (ST), contact angle (CA), and chlorophyll fluorescence responses in redroot pigweed, prickly sida, and barnyard grass. The lowest ST and CA were recorded with L-77 mixed with trifloxysulfuron. Among the six adjuvants, ST and CA were highest with Meth-N-Oil; however, these differences did not greatly influence herbicide efficacy. No trifloxysulfuron adjuvant antagonism was found for any weed species. Differences in activities were observed at 2.5 g/ha trifloxysulfuron with different adjuvants; however, activities were comparable when data were averaged over species and rates. All the adjuvants increased trifloxysulfuron efficacy; some differences were observed among the weed species, but adjuvants were equal in improving trifloxysulfuron efficacy. Redroot pigweed was more sensitive to trifloxysulfuron compared to bamyardgrass and prickly sida was least. Chlorophyll fluorescence 1, 4, 7, and 14 days after treatment (DAT) was not greatly inhibited by trifloxysulfuron mixed with different adjuvants. Reduction in chlorophyll fluorescence was recorded 4 DAT in barnyard grass, but the reduction was not proportionate to the mortality and lacked uniformity among different treatments.