Submitted to: Postharvest Biology and Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: July 17, 2000
Publication Date: N/A
Interpretive Summary: Attempts to find alternatives to chemical control to reduce losses from postharvest decays have been ongoing for some time. Many fungi are becoming more resistant to commonly used fungicides and there is an increasing demand by consumers to reduce chemical residues on produce due to health and environmental concerns. Alternatives to chemical control, when used alone, are generally less effective than fungicides. To increase effectiveness, we combined two non-fungicidal decay control methods: heat treatment and biological control using a bacterium or yeasts. The combined treatment resulted in greater control of blue mold of apple than any of the treatments alone. The apple industry may find that integrating biological control with heat treatment may be a useful alternative to postharvest decay control using fungicides.
'Gala' apples were treated after harvest with heat (38 degrees C for 4 days), wound inoculated with the pathogen Penicillium expansum and the antagonist Pseudomanas syringae or one of two yeast antagonists to reduce postharvest decay. After storage for 7 days at 20 degrees C or 3 months at 1 degree C, the least decay was found on fruit where wounds had been allowed to cure by heat treatment (38 degrees C) or cold storage (1 degree C) for 4 days before inoculation with the pathogen. Addition of any of the antagonists before or after heat treatment further reduced the number and size of the lesions. The highest lesion incidence occurred on apples wounded after heat treatment followed by inoculation with the pathogen. Addition of the yeast antagonists to these fresh wounds reduced the fruit decay as well. While the heat treatment is phytosanitary in that it significantly reduces the pathogen population on the apple surface, it provides little residual protection. The residual protection from the antagonists adds to the control provided by the heat treatment.