Fallow weed control with targeted spray technology

Weed management during the fallow period is a critical component of all vegetable production systems. The use of smart spray technology, which targets herbicide application only where weeds are present, offers potential benefits for reducing herbicide use and costs. Three trials were conducted at the Gulf Coast Research and Education Center in Balm, FL: two in the spring of 2024 (Trials A and B) and one in the fall of 2024 (Trial C). The objective was to assess the efficacy of targeted versus broadcast glyphosate applications with or without pre-emergence flumioxazin. All herbicide treatments significantly reduced total weed density compared to the nontreated control, with no differences observed between broadcast and targeted application technologies. The addition of pre-emergence flumioxazin tended to result in lower weed densities, although the differences were not statistically significant. Reductions in active ingredient usage with targeted glyphosate applications alone compared to broadcast glyphosate, ranged from 13% to 60%, with the greatest reductions observed in fields with the lowest weed densities. When flumioxazin was applied pre-emergence, subsequent targeted glyphosate applications used 33% to 47% less glyphosate compared to broadcast treatments. The use of preemergence flumioxazin reduced subsequent glyphosate use when applied with targeted technology at two of the three sites. However, herbicide costs for targeted glyphosate alone were 79% to 90% lower than for flumioxazin followed by targeted glyphosate. We conclude that targeted application technology can substantially reduce glyphosate use in fallow fields without compromising efficacy. The combination of broadcast preemergence herbicide and targeted post-emergence herbicides tended to reduce herbicide inputs but increased overall herbicide costs.