PROGRAMAS DE ASPERSIÓN DE FUNGUICIDAS EN EL MANEJO DE ROYA (Uromyces viciae-fabae) EN EL VALLE DE TOLUCA.

Abstract

The cultivation of fava beans (Vicia faba L.) is affected by several fungal diseases. One important pathogen due to its reduction of production and quality is rust caused by Uromyces viciae-fabae. Although chemical control is the most frequently utilized strategy, the continuous use of a single mode of action (MoA) or active ingredient favors pathogen resistance. As an alternative, the Fungicide Resistance Action Committee (FRAC) recommends rotation of MoA to slow down this phenomenon. The objective of this study was to evaluate four fungicide MoA rotation programs for the management of rust in fava beans. We established a completely randomized block experimental design with six treatments that included one treatment with constant application of the same active ingredient (clorotalonil), a negative control (no fungicide), and four rotation programs: R1(OxiCu-Cl-Az-Tb), R2(OxiCu-Cl-Az-Ep), R3(Cl-OxiCu-Tb-Az) and R4(Cl-OxiCu-Ep-Az). The design had four replicates, with each experimental unit measuring 7.2 m². We evaluated the variables plant height; incidence, severity, and area under the disease progress curve; yield of green pods; and control efficiency. We found no significant differences among the treatments in plant height during the cycle, although there was a final height difference of up to 16 cm between the rotation treatments and the negative control. Rust appeared 60 days after planting in all treatments. The negative control had the highest incidence, while the R4 program (Cl-OxiCu-Ep-Az) had the lowest area under the disease progress curve over time. The R3 program (Cl-OxiCu-Tb-Az) halted disease incidence at 81 days after planting. In terms of disease severity, the R1 program (OxiCu-Cl-Az-Tb) had the lowest values in the different strata of the plant. The R4 program had the highest yield with 2,995 kg/ha, up to 792% higher than the negative control. However, environmental factors such as high temperatures and the presence of other pathogens, such as Botrytis spp. and Alternaria spp., also influenced the development of the crop. In conclusion, rotations R1 and R4 showed the highest efficiency in controlling rust, constituting a viable strategy for the integrated management of the disease and improving the yield of green fava beans.