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Abstract: ‘Golden Delicious’ apples were wound-inoculated with either Colletotrichum acutatum or Penicillium expansum and then treated with various combinations of heat (38°C) for 4 days, 2% sodium bicarbonate, and two biocontrol agents alone or combined. The fruit were stored for 4 months at 1°C and then at 20°C for 2 weeks. Either heat or the antagonists reduced decay caused by C. acutatum, but a combination of the two was required to completely eliminate decay caused by this pathogen in most cases. Sodium bicarbonate alone or in combination with the antagonists had little effect on C. acutatum. The antagonists alone reduced decay caused by P. expansum but tended to be more effective when combined. Sodium bicarbonate increased the effectiveness of decay control by each antagonist alone or in combination. All of the treatments that included heat virtually eliminated decay caused by this pathogen. The proper combination of alternative control measures can provide an effective strategy to reduce postharvest decay of apple fruit. [Copyright &y& Elsevier]

‘Golden Delicious’ apples were wound inoculated with conidial suspensions of either Colletotrichum acutatum or Penicillium expansum, then treated with heat (38 °C) for 4 days, sodium bicarbonate, and/or one of two heat tolerant biocontrol agents (yeasts). Following four months storage at 0 °C, the apples were left at room temperature for two weeks. Populations of antagonists were stable throughout the experiment and were higher on the heated than the non-heated fruit. Both antagonists reduced decay caused by P. expansum, whereas heat or heat in combination with either antagonist eliminated decay. Either heat or the antagonists alone reduced decay caused by C. acutatum, but a combination of the two was required to completely eliminate decay caused by this pathogen. Adding sodium bicarbonate to the heated or antagonist-treated fruit had little effect on decay caused by either pathogen but when used on non-heated fruit, it significantly reduced decay severity caused by P. expansum after four months at 0 °C. The goal of this research is to combine alternative methods of control to provide an effective substitute for synthetic pesticides. [Copyright &y& Elsevier]

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. [Copyright &y& Elsevier]

‘Golden Delicious’ apples were treated with 1-methylcyclopropene (MCP) or kept at room temperature for the duration of the MCP treatment. After the MCP treatment, they were wounded and inoculated with the pathogen Penicillium expansum or with P. expansum and a heat tolerant yeast (antagonist). After incubation at room temperature for up to 48 h, the apples were treated with heat at 38 °C for 4 days, and/or moved to cold storage for up to 5 months. Heat had an eradicative effect, when the pathogen was allowed to incubate in the apple wounds for 6 or 12 h after inoculation, resulting in less decay than at any other incubation time. The highest decay incidence occurred on the control that was inoculated with the pathogen and placed in cold storage. The least decay incidence and the smallest lesion diameter occurred on apples treated with a combination of the antagonist plus heat or heat alone. In general, MCP-treated apples had a higher lesion incidence, but similar lesion severity compared with non-MCP-treated apples. Only in the combination treatment of heat plus the antagonist, when the incubation time of the pathogen was between 6 and 24 h, was the lesion diameter slightly larger on MCP-treated fruit than on fruit not treated with MCP. This difference between the MCP-treated apples and non-MCP-treated apples decreased during storage. Antagonist populations in the apple wounds were stable or increased for all treatments. They were higher on MCP-treated apples than on non-MCP-treated apples and they increased with increasing incubation periods at room temperature after inoculation. Antagonist populations on apples heat treated after inoculation were higher than those kept at room temperature immediately after the heat treatment and after 3 months storage. The heat treatment had an eradicative effect, whereas the antagonist had a protective effect. The combination of heat and antagonist was more effective than either treatment alone, even when there was a delay of the heat treatment for up to 24 h. The combination of these two control measures, therefore, was complementary and resulted in better decay control than either treatment alone. [Copyright &y& Elsevier]

Abstract: ‘Golden Delicious’ apples were wound-inoculated with Penicillium expansum and treated with various combinations of sodium bicarbonate and two antagonists (Metschnikowia pulcherrima, Cryptococcus laurentii), and then stored in air or controlled atmosphere (CA=1.4kPa O2 and 3kPa CO2) for 2 or 4 months at 1°C. The antagonists survived and their populations increased during both air and CA storage. The antagonists alone reduced blue mold but were more effective when combined. Sodium bicarbonate tended to reduce lesion size when used with these antagonist, either when they were used alone or combined. Storage under CA conditions also increased the effectiveness of both antagonist, when used alone or in combination. The only treatment that completely eliminated P. expansum-incited decay was the combination of the two antagonists and sodium bicarbonate on fruit stored under CA conditions. The proper combination of alternative control measures can provide commercially acceptable long-term control of fruit decay and could help reduce our dependency on fungicides. [Copyright &y& Elsevier]