Control of bitter rot and blue mold of apples by integrating heat and antagonist treatments on 1-MCP treated fruit stored under controlled atmosphere conditions

Abstract

To maximize control of fruit decay by alternatives to synthetic fungicides after harvest, various control strategies can be integrated. Treatment of fruit with antagonists is one of the most promising alternatives. This treatment, however, has little or no eradicative activity, which limits its use. Fruit treatment with hot air (at 38 °C) for 4 d has eradicative but no residual activity against blue mold (caused by Penicillium expansum ) on apple, and 1-methylcyclopropene (1-MCP) is an ethylene receptor inhibitor which slows apple maturation and, presumably, extends action of natural defense mechanisms. An antagonist, Metchnikowia pulcherrima T5-A2, was used in combination with heat and 1-MCP treatments to control bitter rot (caused by Colletotrichum acutatum ) and blue mold (caused by P. expansum ) on ‘Golden Delicious’ apples under controlled atmosphere (CA) conditions. 1-MCP treatment increased bitter rot and blue mold decays, but both of these decays were effectively controlled on 1-MCP treated apples by a combination of the antagonist and heat treatments. C. acutatum is a weaker pathogen than P. expansum , and bitter rot, even on the control treatments, developed only after 4 months in CA storage followed by 2 weeks incubation at 24 °C. In contrast, non-treated fruit inoculated with P. expansum were completely decayed after 2 months in CA. The antagonist controlled bitter rot more effectively than blue mold, while blue mold was more effectively controlled by heat treatment. The use of 1-MCP on harvested fruit to inhibit maturation can predispose fruit to decay, but the alternatives to synthetic fungicides are capable of preventing this increase in decay.