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United States Department of Agriculture

Agricultural Research Service

Research Project: Alternatives to methyl bromide soil fumigation for vegetable and floriculture production

Location: Subtropical Plant Pathology Research

Title: Control of Phytophthora capsici in greenhouse-grown peppers with biorational compounds

Authors
item Yandoc-Ables, Camilla -
item Rosskopf, Erin
item Hong, Jason
item Burelle, Nancy
item Albano, Joseph
item Lamb, Elizabeth -

Submitted to: Plant Health Progress
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: September 20, 2012
Publication Date: N/A

Interpretive Summary: Phytophthora capsici is an oomycete pathogen of bell peppers that causes devastating crop losses. The pathogen is resistant to some of the most widely-used chemical control measures, thus, biologically-based management strategies would be useful to growers of bell pepper. A series of experiments were conducted to determine if various biological control and biorational materials could control the disease under different pathogen inoculum concentrations and fertility regimes. The material known as FNX-100 and now sold under the trade name BioPhos, composed of dipotassium phosphate and dipotassium phosphonate was found to provide consistent control of the disease when tested in the greenhouse. Foliar applications of the material were ineffective and caused phytotoxicity, while drench applications were highly effective, regardless of inoculum concentration or fertility regime. This material was compared to several other phosphate-based materials and only K-Phite was found to provide similar control.

Technical Abstract: Several commercially available biopesticides and phosphonate-containing products were selected and tested for their efficacy in controlling Phytopthora capsici on bell pepper at various inoculum and fertility levels. The effects of concentration, application method and frequency of application on the efficacy of phosphonates were deteremined, and the efficacy and toxicity of selected commercially available phosphonate-containing products against Phytophthora root rot on bell pepper was tested. The efficacy of four commercially manufactured biopesticides was tested against increasing concentrations (50, 500, and 5,000 zoospores/plant) of Phytopthora capsici. In a second series of experiments, six biopesticides and an untreated control along with four fertilizer concentrations were tested to determine if there was an interaction between plant fertility and disease control wtih the biorational materials. From these experiments, it was determined that, while increased inoculum concentration had a significant impact on disease severity, there was no interaction with biopesticide treatment. Only the phosphonate-based material provided disease control. Fertility had no impact on disease control. Since the phosphonate material was the only product that provided consistent disease control, application method and frequency of application of this material was investigated. Drench applications significantly reduced disease levels in pepper, without causing any phytotoxic damage, while foliar applications did not control disease. Six different phosphate- or phosphonate-based materials were compared for their ability to control this disease when applied to foliage or as a drench. Only FNX-100 (BioPhos) and K-Phite provided control when applied as a drench treatment.

Last Modified: 4/17/2014
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