ROTACIÓN DE FUNGICIDAS POR MODOS DE ACCIÓN (MoA), PARA EL CONTROL DE PUDRICIÓN RADICULAR (Rhizoctonia solani) EN Vicia faba L.

Abstract

The objective of the present study was to evaluate proposed rotations of fungicides that differ in their mode of action (MoA) for the control of root rot caused by Rhizoctonia solani in fava beans. The experiment was performed under field conditions. We evaluated five rotation treatments: T1 (Ip+D-A+Ca+F-A+Be), T2 (D-A+Ca+F-A+Be+Ip), T3 (Ca+Ip+F-A+Be+D-A), T4 (Be+Ip+F-A+D-A+Ca), T5 (F-A+Ip+D-A+Be+Ca), as well as a non-treated negative control (T6) and a positive control treated only with Captan (T7). The treatments were distributed in a randomized complete block experimental design with four replicates. For each treatment, we applied the corresponding fungicide once every 7 days, with two consecutive applications of each fungicide, in the order noted above. We evaluated the incidence of the disease, and the height, yield, and biological efficiency of the plant to determine which rotation best controlled the disease and least affected fava bean yield. The incidence data were analyzed using the program R to estimate the area under the disease progress curve over time per replicate, per treatment. The area under the curve values were analyzed in the program SAS to perform an analysis of variance, and in the case of significant differences, we performed Tukey’s mean separation test at 0.05%. The results indicated the existence of significant differences among the different rotations, in that some rotations more effective than others at reducing disease incidence. Rotation T3 (Captan (Ca), Iprodione (Ip), Fluazinam (F), Benomyl (Be) and Difenoconazole (D)) reduced disease progression over time, making it the most rotation effective against Rhizoctonia solani. None of the MoA rotations negatively affected plant growth, and some of the most effective rotations for control showed a slight increase in plant growth relative to the negative control. The positive control (Captan) had the highest yield. The T3 rotation had the highest biological efficiency, 54% higher than the negative control. The results showed that the biological efficiency of the rotations depended on the sequence or timing of application of fungicides with different MoA, compared to the constant application of Captan in the positive control. This could be due to the phenological stage of the fava bean and the expression of the disease. The finding that the T3 MoA rotation had adequate biological efficiency suggests that this rotation is a viable alternative for control while preventing fungicide resistance. Our results show that rotating fungicides with distinct MoA is a key strategy for controlling root rot caused by Rhizoctonia solani in an efficient and sustainable way.