BIN DRENCHING SYSTEM FOR TESTING BIOCONTROL AGENTS AND CHEMICALS FOR CONTROL OF POSTHARVEST DECAY OF APPLES UNDER COMMERCIAL CONDITIONS

Authors: Janisiewicz, Wojciech; Peterson, Donald; YODER, KEITH - VIRGINIA POLYTECHNIC INST; Miller, Stephen

Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/20/2004
Publication Date: 5/1/2005
Citation: Janisiewicz, W.J., Peterson, D.L., Yoder, K., Miller, S.S. 2005. Bin drenching system for testing biocontrol agents and chemicals for control of postharvest decay of apples under commercial conditions. Plant Disease. 89:487-490

Interpretive Summary: Beneficial bacteria and yeasts that can control fruit decays have been applied to apples after harvest by spraying, dipping, and drenching. The method of application has a significant effect on the efficacy of the decay control. Spraying or dipping applications have been evaluated often in the past but bin drenching has rarely been evaluated because it requires large amounts of fruit and a considerable amount of treatment suspension with the beneficial bacteria or yeast. This makes drenching tests very expensive and often technically prohibitive for most laboratories. A portable drencher capable of drenching a single bin of fruit was built to simulate the commercial application of chemicals to harvested apples in small orchard operations in the Central and Eastern United States. The drencher required as little as 125 L of the treatment solution, permitted various bin travel speeds, and allowed for frequent change of the treatments. Wounded apples that were placed midway between the bottom and top of the bin and were drenched with suspension containing fungus causing blue mold decay had a high incidence of decay after 3 months in cold storage. Treatment with the beneficial yeast resulted in significant reduction of the fruit decay, and the addition of sodium bicarbonate (baking soda) further reduced decay to negligible levels on 'Golden Delicious' apples. This portable drencher can be very useful in evaluating beneficial organisms for ability to control fruit decay by drenching application, and may also be used for treating fruit with beneficial microorganisms and chemicals in small commercial operations.

Technical Abstract: A portable drencher capable of drenching a single bin of fruit was built to simulate the commercial application of chemicals to harvested apples in small orchard operations in the Central and Eastern United States. The drencher required as little as 125 L of the treatment solution and permitted various bin travel speeds. Wounded apples were placed midway between the bottom and top of the bin in the center and near the four corners of a bin (20 fruit per place) and covered with apples to fill the bin. The bins were drenched with a suspension containing P. expansum at 2x104 conidia/ml in 2000, 5x103 conidia/ml in 2001, or 3x103 conidia/ml in 2002 and 2003 . In 2000 and 2003 the additional treatments included a combination of P. expansum with the yeast M. pulcherrima at ~ 1.2x107 CFU/ml, and in 2003 a combination with 2% sodium bicarbonate or a mixture of the yeast and soda bicarbonate. After 3 months of storage at ~2 C, at all P. expansum concentrations, more than 90 % of wounded fruit developed decay on 'Golden Delicious', 'Delicious' and 'Rome' apples in the 2000-2002 experiments. In 2003, 66% and 33.1 % of the wounded fruit developed decay on 'Delicious' and 'Golden Delicious', respectively. The, application of the antagonist reduced decay to 39% and 3.3 % on 'Golden Delicious' in 2000 and 2003, respectively, and to 26% on 'Delicious' in 2003. The addition of SB reduced decay on both cultivars, and in combination with the yeast, was the most effective treatment on 'Golden Delicious'. This portable drencher can be very useful in evaluating different treatments applied to apples after harvest at the commercial level.