Efficacy of biocontrol agents and bactericides in control of pepper bacterial spot

Abstract

Bacterial spot caused by Xanthomonas euvesicatoria is considered one of the most important diseases of pepper in Serbia. In order to control this disease, copper based compounds (copper hydroxide, copper oxychloride, copper hydroxide + mancozeb, copper oxychloride + mancozeb), antibiotics (streptomycin sulfate and kasugamycin), resistance inducer (acibenzolar-S-methyl), antagonistic bacteria Bacillus subtilis (strains QST 713 and AAac), bacteriophage (strain K Phi 1) and one commercial microbial fertilizer, were tested for efficacy and compared to untreated control. The experiments were carried out in a greenhouse and climatic chamber conditions. Plants were inoculated with X euvesicatoria strain KFB 13 (10(8) CFU mL(-1)) using hand-held sprayer. Results of three experiments showed that all treatments except microbiological fertilizer significantly reduced intensity of bacterial spot symptoms compared to the untreated control. The most efficient treatment was acibenzolar-S-methyl reducing disease severity 93-97%. There was no statistically significant difference in efficacy of this treatment and copper hydroxide, copper oxychloride, copper hydroxide + mancozeb, copper oxychloride + mancozeb, streptomycin sulfate, kasugamycin and antagonistic strain QST 713 treatments. Application of antagonistic strain AAac and bacteriophage K Phi 1 significantly reduced disease intensity but less than the first group of treatments. Bacteriophage K Phi 1 (78-85% rH) was more effective in the climatic chamber compared to the efficacy (38% rH) in the greenhouse experiments.