Application factors affecting foliar spray loss for floating aquatic plants

• Published in: Journal of aquatic plant management 2024-01, Vol.62 (2), p.53-59
• Main Authors: Sperry, Benjamin P, Mudge, Christopher R, Durham, Michael W, Getsinger, Kurt D
• Format: Article
• Language: English
• Subjects: Aquatic plants; Best management practices; Dyes; Experiments; Floating; Floating plants; Freshwater plants; Herbicides; High density polyethylenes; Nozzles; Pistia stratiotes; Retention; Rivers; Spray deposition; Spray guns; Tracers; Water; Water circulation; Water column
• ISSN: 0146-6623
• DOI: 10.57257/JAPM-D-24-00008

Mesocosm experiments were conducted in 2020 and 2021 in Louisiana and Florida to evaluate the effects of foliar spray application factors on spray deposition patterns for applications to floating aquatic plants using tracer dye. In the first experiment, spray trajectory and associated impact angles were investigated. A forward spray trajectory angle of 90 decreased spray loss by 22% to the water column when targeting waterhyacinth [Eichhornia crassipes (Mart.) Solms], compared to downward 90 and forward 45 spray angles. However, no difference in spray loss was detected for waterlettuce (Pistia stratiotes L.) among tested spray trajectory angles. The second experiment tested spray pattern (single-nozzle cone via spray-gun, single-nozzle straight stream via spray-gun, and multinozzle broadcast boom) effects on spray loss for applications to waterhyacinth, water lettuce, and giant salvinia (Salvinia molesta D.S. Mitchell). For waterhyacinth, spray loss was greatest with single-nozzle cone (51%), followed by singlenozzle straight stream (34%), followed by broadcast boom (25%). However, spray loss for waterlettuce was greatest using single-nozzle straight-stream applications (61%) and lowest with broadcast boom (40%) and single-nozzle cone (35%) applications. Spray loss for giant salvinia was greatest for single-nozzle cone applications (32%) and least for broadcast boom applications (19%). A third experiment tested spray loss between broadcast boom and spray-to-wet spray-gun application techniques; no differences were observed between techniques in applications to waterhyacinth or waterlettuce. These results suggest that foliar spray loss when targeting common floating aquatic plants can be minimized by manipulating application parameters and likely requires species-specific considerations. These results require verification under operational field conditions to develop best management practices to reduce spray loss for foliar-applied aquatic herbicide applications.