Improving Control of Green and Blue Molds of Oranges by Combining Pantoea Agglomerans (CPA-2) and Sodium Bicarbonate

The potential of using Pantoea agglomerans (strain CPA-2) alone, or in combination with sodium bicarbonate or sodium carbonate solutions, for control of Penicillium digitatum (green mold) and Penicillium italicum (blue mold) on oranges was investigated under ambient (20 °C) and cold storage (3 °C) conditions. P. agglomerans controlled both pathogens on oranges at 2 × 10⁸ cfu ml^-1. The biocontrol agent was found to be completely tolerant to 2% sodium bicarbonate at room temperature, although its culturability was reduced by > 1000-fold after 30 min in 2% sodium carbonate. The efficacy of P. agglomerans for control of green mold was improved when combined with sodium bicarbonate, resulting in complete and 97.6% reduction of decay incidence at 3 °C and 20 °C, when compared to untreated controls. Satisfactory results were also obtained with the combined treatment for control of blue mold. P. agglomerans grew well inside wounds on oranges at both 20 °C and 3 °C. In contrast, it showed a reduced growth on the surface of intact fruit. Sodium bicarbonate at 2% concentration did not noticeably affect antagonist population development. Thus, use of bicarbonate treatment at 2% followed by the antagonist P. agglomerans CPA-2 could be an alternative to chemicals for control of postharvest diseases on oranges.