Compost Tea as a Disease Control for Downy Mildew (Peronospora belbahrii) and Nutritional Supplement in Sweet Basil (Ocimum basilicum)

Abstract

Growing concern on the use of inorganic fertilizers and pesticides has pushed investigators to find agro-ecological alternatives due to their impact on our environment and agriculture overall. Compost tea is a tool that has proven to be effective in controlling different plant pathogens. The aim of this study was to evaluate its effectiveness in suppressing Peronospora belbahrii, an oomycete responsible for the most common disease on organic basil produced in Zamorano, where no alternatives to fungicides have been found. A compost tea brewer was built. Foliar and foliar + soil applications were evaluated as well as Bacillus subtilis, salicylic acid and peracetic acid in a continuous experiment of eight weeks. Plants were inoculated with the pathogen; treatment applications as well as disease severity evaluations were made weekly and yield was recorded at week 4 and 8. Foliar spraying of compost tea reduced disease severity significantly when compared to the no application control in only one of the eight weeks. Foliar + soil spraying did so in only two of the eight weeks. The other treatments were not different from the control. Foliar + soil spraying of compost tea had significantly higher yields at week 4 with 48.23 ± 6.2 g/plant and higher at week 8, but not significant. The reduced affectivity of the compost tea was attributed, in part, to an elevated level of nutrients during the brewing process allowing high microorganism growth that resulted in fast oxygen consumption which could account for the lower compost tea quality.

Ceiba, 2012. Volumen 53(1):17-29