Spray volume and droplet spectrum in the control of Bidens pilosa and Ipomoea triloba with the Fomesafen herbicide ¹

Volume de calda e espetro de gotas no controle de Bidens pilosa e Ipomoea triloba com o herbicida Fomesafen

ABSTRACT

Among weed control methods, chemical control using herbicides is one of the most widely employed due to its practicality and efficiency. However, there is still a lack of reliable information regarding the effectiveness of low-volume spraying and the droplet spectrum for contact herbicides, such as fomesafen. The objective was to determine the spray volume and droplet spectrum for applying the fomesafen herbicide and its efficacy in controlling hairy beggarticks (Bidens pilosa) and littlebell (Ipomoea triloba). The herbicide was applied using a CO₂-pressurized knapsack sprayer with TT11002 spray tip spaced at 0.50 m, operating at pressures of 100 kPa (very coarse droplets) and 400 kPa (medium-sized droplets) with spray volumes of 35, 70, 140, and 280 L ha^-1, obtained by varying the application speed. At the time of application, the percentage of covered area and droplet density (droplets cm^-²) were evaluated on water-sensitive paper labels using the DropScope^® program. The best control results for hairy beggarticks were achieved when the application was performed with very coarse droplets at a pressure of 100 kPa, with a spray volume between 65 and 280 L ha^-1, droplet density exceeding 60 droplets cm^-2, and coverage greater than 10%. Fomesafen does not provide effective control of littlebell.

Key words:
low-volume; coverage; droplet density

HIGHLIGHTS:

Spray volumes greater than 65 L ha^-1 with very coarse droplets promote satisfactory control of hairy beggarticks.

Fomesafen applied with a coverage percentage exceeding 10% provides satisfactory control of hairy beggarticks.

Fomesafen dose of 0.25 kg a.i. ha^-1 does not satisfactorily control littlebell plants.