Fungicidas sistêmicos combinados a agentes de controle biológico e aplicação zero no controle de ferrugem asiática da soja

Abstract

There are several factors limiting the soybeans cultivation in Brazil, highlighting diseases such as Asian rust, which has a highly destructive potential. Due to the constant use of systemic fungicides for its control, a regression in their efficiency is noted due to the development of insensitivity on the part of the pathogen. The application of fungicides in advance (V0 application) is a technique that has been used to maximize the control of this and other diseases. The use of biological control agents, combined with V0 application, in the control of Asian rust and soybean yield were evaluated. The experiment was conducted in UFFS - Campus Erechim experimental area, in the 2023/24 crop season, in a randomized block design, with a 6 x 2 + 1 factorial scheme, being: treatments x with and without zero application (V0) + control (without application of fungicides), with 4 repetitions and 13 treatments. The treatments consisted of a control without application (T1); treatments only with the use of systemic fungicides, without and with V0 (T2 and T3, respectively); biological control agents combined with systemic fungicides without V0 (T4, T5, T6, T7, T8) and with V0 (T9, T10, T11, T12, T13). The disease severity and control (%), and defoliates were evaluated; number of pods per plant (NPP); number of grains per plant (NGP); thousand grains weight (TGW, g) and crop productivity (kg ha-1). The greatest control was observed in T12 and T13 treatments, differing only from the control. For NPP and NGP, no statistically significant difference was found. The use of V0 in T3 treatment increased the TGW compared to T2. In relation to defoliation, the lowest levels occurred in treatments combined with biological control agents, followed by those containing only systemic fungicides, differing from each other and from the control. As for productivity, any biological control agent tested, associated with systemic fungicides without V0, results in an average increase of 340 kg ha-1 (5.6 bags) compared to T2 (31.4 bags), in BMX Ativa RR cultivar.