Unoccupied aerial application systems (UAAS) are gaining popularity for weed management to increase applicator safety and to deliver herbicide treatments where treatment sites limit ground-based spray equipment. Several studies have documented UAAS application strategies and procedures for weed control in terrestrial settings, yet literature describing remote spray technology for use in aquatics remains limited. Currently, applicators seek guidance for UAAS deployment for aquatic weed management to overcome site access restrictions, deal with environmental limitations, and improve ground-based applicator safety in hazardous treatment scenarios. In the present case studies, we evaluate a consumer-available UAAS to deliver the herbicide, florpyrauxifen-benzyl, as both foliar and directed in-water spray applications. The first case study showed that the invasive floating-leaved plant, yellow floating heart, was controlled 80% to 99% by 6 wk after treatment (WAT) following UAAS foliar herbicide treatments. The second case study demonstrated that UAAS directed in-water herbicide application reduced variable-leaf watermilfoil visible plant material by 94% at 5 WAT. Likewise, directed in-water applications from UAAS eliminated the need to deploy watercraft, which improved overall operational efficiency. Data from both case studies indicate that UAAS can provide an effective and efficient treatment strategy for floating-leaved and submersed plant control among common herbicide treatment scenarios. Future integration of UAAS in aquatic weed control programs is encouraged, especially among smaller treatment sites (≤4 ha) or where access limits traditional spray operations.

Nicosulfuron efficacy varies with surfactant, natural salts in the spray water carrier, and added nitrogen fertilizer salts. Scanning electron micrographs (SEM) were taken of nicosulfuron spray droplet residue on large crabgrass in the greenhouse. Spray residue characteristics differ for nicosulfuron applied with surfactants alone and with specific salts. Uniform deposits with close contact to the leaf epicuticular surface generally related positively to nicosulfuron efficacy. Ammonium salt enhancement of nicosulfuron phytotoxicity when with surfactant X-77® related to a change from a ring to a uniform deposit. Spray mixtures containing Tween 20 or Atplus 300F surfactants that gave distinct dark amorphous deposits over anticlinal cell walls generally related to effective nicosulfuron treatments. Salts that were antagonistic to nicosulfuron phytotoxicity left a large amorphous deposit, including ammonium nitrate antagonism of nicosulfuron applied with Pluronic® P85 surfactant and general antagonism from sodium bicarbonate. The SEM information indicates that the effect of surfactants and salts on spray deposit characteristics influence nicosulfuron efficacy.