Integration of biological and conventional treatments in control of pepper bacterial spot

Abstract

Bacterial spot caused by Xanthomonas euvesicatoria is one of the most devastating pepper diseases in Serbia. Questionable seed quality, climatic conditions, and frequent irrigation during summer favour the disease occurrence and spread. The available management practices do not provide adequate disease control. Therefore, development of alternative and more sustainable disease management strategies is needed. Integration of classical and biological treatments could be an effective, environmentally safe option for reducing pepper bacterial spot severity. In order to develop an efficient integrated disease management program, we studied efficacy of biocontrol agents (bacteriophage strain K Phi 1 and two strains of Bacillus subtilis AAac and QST 713), systemic acquired resistance (SAR) inducer (acibenzolar-S-methyl - ASM), a commercial microbial fertilizer (Slavol), copper based compounds (copper hydroxide and copper oxychloride) in combination with or without mancozeb, and antibiotics (streptomycin sulphate and kasugamycin). They were applied as single treatments in two separate field experiments. Based on the single treatment efficacy, various combinations of the treatments were chosen for further testing in three separate field experiments. Additionally, we evaluated potential negative effect of ASM on pepper growth and yield in the growth chamber experiment. All the tested single treatments significantly reduced disease severity compared to the inoculated control (IC), except microbiological fertilizer and the antagonistic strain AAac. Integration of copper hydroxide, ASM and bacteriophages was the most efficient treatment, reducing the disease intensity by 96-98%. The results indicated that this combination may be an adequate alternative program for control of pepper bacterial spot.