Management of coffee leaf rust using L-glutamic acid biofertilizer combined with fungicide

Abstract

The use of biofertilizers is a potential tool for the management of crop diseases. Coffee leaf rust, which is commonly controlled by triazole and strobilurin fungicides, is one of the main phytosanitary challenges associated with coffee cultivation. However, the indiscriminate use of such fungicides may be harmful to the environment and human health, in addition to having a negative impact on coffee exports. The aim of this study was to evaluate the effect of foliar application of L-glutamic acid on the incidence and severity of coffee leaf rust in the southern region of Minas Gerais, Brazil. A biofertilizer made of sugarcane molasses fermented by the bacterium Corynebacterium glutamicum was used in combination with 25% L-glutamic acid and a fungicide of the triazole group registered for crops. The experimental design adopted was randomized blocks with four replications (eight plants per replicate) and seven treatments: fungicide, control test, 0.8 L ha-1 of biofertilizer, combinations of 0.04, 0.06, 0.08, and 0.1 L ha-1 of biofertilizer and fungicide. Three treatments were initially applied in a preventive way, before the rainy season, and then at intervals of 60 days. After seven months of treatment, we observed that coffee leaf rust incidence was significantly lower in coffee plants treated with combined products than in treatments of either fungicide or biofertilizer only, with a reduction of 56% and 45%, respectively, being observed. Among the combinations of biofertilizer and fungicide, coffee leaf rust incidence reduced with an increase in the biofertilizer dose, such that the disease incidence in plants treated with a dose of 0.1 L ha-1was 58% lower than that in plants treated with fungicide only. No differences in disease severity were observed among the treatments. In conclusion, the use of a combination of biofertilizer and fungicide is more effective for the management of coffee leaf rust than the use of the isolated products.