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ARS Home » Southeast Area » Poplarville, Mississippi » Southern Horticultural Research Unit » Research » Publications at this Location » Publication #368371

Research Project: Production and Disease and Pest Management of Horticultural Crops

Location: Southern Horticultural Research Unit

Title: Control of Pseudomonas amygdali pv. loropetali on metal, wood, and Loropetalum chinense stem surfaces

item Copes, Warren
item MAVRODI, OLGA - Mississippi State University
item MAVRODI, DMITRI - University Of Southern Mississippi

Submitted to: Plant Health Progress
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/19/2019
Publication Date: 3/1/2020
Citation: Copes, W.E., Mavrodi, O.V., Mavrodi, D.V. 2020. Control of Pseudomonas amygdali pv. loropetali on metal, wood, and Loropetalum chinense stem surfaces. Plant Health Progress. 20(4):270-277.

Interpretive Summary: Bacterial gall is a relatively new disease problem on Loropetalum cultivars in commercial plant nurseries. Currently, few products have been tested for their efficacy to kill the bacterial pathogen, Pseudomonas amygdali pv. loropetali. Several commercial disinfestants were tested on stainless steel, pressure-treated wood and Loropetalum stem surfaces. Based on these trials, EPA label recommended rates of Clorox® Germicidal Bleach, Green Shield® II, KleenGrow™, and Virkon® S will disinfest metal surfaces of P. amygdali pv. loropetali, while only Clorox® Germicidal Bleach and Virkon® S will comparably disinfest pressure-treated wood surfaces. Clorox® Germicidal Bleach appears to be suitable for treating vegetative stem cuttings, but additional research is needed before this practice can be recommended. This research established rates of commercial disinfestants that can be used by Loropetalum growers to treat contaminated production areas. University Extension workers and crop advisers can incorporate this information into their recommendations.

Technical Abstract: Clorox® Germicidal Bleach, Cuproxat®, Green Shield® II, KleenGrow™, Virkon® S and ZeroTol® 2.0 were evaluated for their ability to inactivate Pseudomonas amygdali pv. loropetali on stainless steel (SS), pressure-treated wood (PtW), and Loropetalum stem sections. Clorox® at 11% product and Virkon® S at 1.0% product eliminated P. amygdali pv. loropetali on SS surfaces and nearly eliminated it on PtW surfaces. Green Shield® II at 0.5% and KleenGrow™ at 0.8% were effective to a lesser degree on SS and PtW. Cuproxat® and ZeroTol® 2.0 were not effective against this bacterium in these applications. Clorox® and KleenGrow™ were evaluated further for their ability to kill P. amygdali pv. loropetali on Loropetalum stems, which was used as a preliminary surrogate for vegetative stem cuttings. Only Clorox® eliminated bacteria from stem surfaces, but the bacterial inoculum level appeared to affect efficacy. Several disinfestants are commercially available that will kill P. amygdali pv. loropetali on production surfaces.