Field Control of Phytophthora Blight of Pepper Plants with Antagonistic Rhizobacteria and DL-$\beta$-Amino-n-Butyric Acid

Treatment with antagonistic rhizobactera Burkholderia cepacia strain N9523 or an inducer of resistance DL-$\beta$-amino-n-butyric acid (BABA) effectively inhibited Phytophthora capsici infection on pepper plants in artificially infested pots. Treatment with BABA alone at $1,000\mu\textrm{g}$/ml or together with B. cepacia in combination induced a strong protection from the Phytophthora disease in the greenhouse. In artificially infested field, protection of pepper plants against the Phytophthora epidemic by BABA treatment was maintained at a considerable level. In contrast, soil drench with the antagonist B. cepacia alone, or in combination with BABA did not suppress the Phytophthora epidemic in the field. Mortality of pepper plants caused by P. capsici infection was significantly reduced by treatment with the antagonist Pseudomonas aeruginosa strain 950923-29 and BABA (12-29% plants diseased) relative to the untreated control (41-91% plants diseased) in the naturally infested field. Treatment with the antagonist Ps. aeruginosa strain 950923-29 and BABA also resulted in high levels of protection against Phytophthora blight in pepper plants. In the plastic filmhouse test, the average percentage of plants diseased was significantly low relative to the naturally infested field. Treatment with the antagonist Ps. aeruginosa strain 950923-29 and BABA in combination was most effective in suppressing the Phytophthora disease in field and plastic filmhouse.