EFEITO DO VOLUME DE APLICAÇÃO NA EFICÁCIA DE HERBICIDAS UTILIZADOS NO CONTROLE DE Conyza spp. EM CONDIÇÕES DE CAMPO

Abstract

Inadequate weed control is one of the main factors responsible for reduced agricultural yield. Among the most relevant species, horseweed (Conyza spp.) stands out, characterized by high seed production, wide dispersal capacity, and the occurrence of biotypes resistant to different herbicide modes of action in Brazil. Although resistance is often associated with the repeated use of herbicides with the same mechanism of action, control failures may also be related to operational and environmental factors, including spray volume, climatic conditions, water quality, application technology, and soil characteristics. In this context, the present study aimed to evaluate the influence of different contact herbicides and spray volumes on the efficiency of chemical control of Conyza spp. The experiment was conducted under field conditions in the municipality of Mandaguari, Paraná State, Brazil, using a randomized complete block design in a 4 × 5 factorial arrangement, consisting of four herbicides (diquat, ammonium glufosinate, saflufenacil, and tiafenacil) and five spray volumes (50, 100, 150, 200, and 250 L ha⁻¹), with three replications. The plots had a natural infestation of horseweed plants approximately 0.5 m tall. Overall, the results indicated that control efficiency was more closely related to the herbicide used than to the spray volume applied. Saflufenacil showed the most consistent performance throughout the evaluations, followed by ammonium glufosinate, whereas diquat and tiafenacil exhibited lower persistence and lower control percentages in the final assessments. Higher spray volumes provided a faster initial control response; however, they did not result in significant differences in final control. It can be concluded that proper herbicide selection is crucial for the effective management of Conyza spp., and reduced spray volumes can be used without compromising efficacy, provided that appropriate application technology is adopted.