Assessment of disinfectants for control of Phytophthora ramorum

ASSESSMENT OF DISINFECTANTS FOR CONTROL OFPHYTOPHTHORA RAMORUM

Assessment of disinfectants for control of Phytophthora ramorum

Heather Hammack, M.S.Graduate Research Assistant

Steven E Newman, Ph.D.Greenhouse Crops Extension Specialist and Professor of Floriculture

Craig Ramsey, Ph.D.USDA-APHIS-PPQ-CPHST

ProGreen EXPO11 February 2014

Assessment of disinfectants for control of Phytophthora ramorum

• Collaborative project between:– CSU Agricultural Experiment Station– USDA-APHIS Center for Plant Health Science and

Technology

Team

• Steven E. Newman – co-principal investigator• Craig Ramsey – co-principal investigator• Heather Hammack – MS horticulture student• Vanessa Sandoval – MS horticulture student• Debra Newman – research associate• Paul Freebury – research associate

Goals of this project

• Test oxidant disinfectants for decontamination of greenhouse supplies, contaminated soil, and infected plants that are contaminated with a fungal surrogate for P. ramorum.

• The main objectives of this project are to determine: – efficacy of oxidants on greenhouse supplies and equipment,– decontamination of greenhouse soil, and – phytotoxicity of oxidants to selected nursery plants.

Phytophthora ramorum

• Sudden oak death carried by (P. ramorum) is a fungal pathogen that infects over 120 plant hosts and is threatening shrub propagation in many U.S. nurseries.

• Oomyctes in the genus Phytophthora are the most destructive plant pathogens in agricultural and nursery production today.

Phytophthora ramorum

• Spore structures from this pathogen can survive in water and soil, which allows them to be widely dispersed by natural causes and by national transportation networks.

• Inorganic disinfectants based on oxidant chemistry have a low risk of inducing microbial resistance due to their multi-site, mode of action.

From:Scott Pfister, DirectorForest Pest ProgramsUSDA APHIS PPQ

From:Scott Pfister, DirectorForest Pest ProgramsUSDA APHIS PPQ

DisinfectionCommon industrial oxidizers and their potential relative to chlorine

OxidantOxidation potential

(mV)Oxidation relative to

chlorine

Fluorine 3,050 2.25

Ozone 2,070 1.52

Hydrogen peroxide 1,780 1.31

Potassium permanganate 1,680 1.25

Chlorine dioxide 1,570 1.15

Chlorine 1,360 1.00

Bromine 1,070 0.70

DisinfectionPathogen survival from laboratory simulations and

hydrocooler studies according to Suslow (2003)

Pathogen

Survival at ORP (mV)

< 485 550<X<620 >665

E. coli O157:H7 > 300 s < 60 s < 10 s

Salmonella spp. > 300 s > 300 s < 20 s

L. monocytogenes > 300 s > 300 s < 20 s

Thermotolerant coliform > 48 hr > 48 hr < 30 s

Lang, J. M., Rebits, B., Newman, S. E., and Tisserat, N. 2008. Monitoring mortality of Pythium zoospores in chlorinated water using oxidation reduction potential. Online. Plant Health Progress doi:10.1094/PHP-2008-0922-01-RS.

Heather Hammack’s MS Thesis Research

Objectives

• Evaluate Camellia japonica ‘Scentsation’ foliage response sprayed with chlorine dioxide solution at three different concentrations, with and without the surfactant Sarcosinate, with a negatively charged electrostatic low volume sprayer.

Objectives

Determine the impact of five consecutive spray applications on the photosynthetic plant health of Camellia japonica ‘Scentsation’ and maximum quantum efficiency fluorescence analysis (Fv/Fm)

Objectives

Assess Camellia japonica ‘Scentsation’ plant marketability after spray applications using a visual injury rating scale

Methods

Two oxidants: chlorine dioxide (ClO2) at three rates 0, 100, 200, and

400 ppm – Electro-Biocide: Strategic Resource Optimization, Inc.

hydrogen dioxide (H2O2) at two rates, 0 and 100 ppm – OxiDate 2.0: BioSafe Systems, Inc.

Two surfactant rates – 0 and 0.2% sarcosinate Five foliar application dates at three-day intervals

Methods

Visual assessments: Three days after each of the five successive spray

applications Six and 14 days following the final spray

application

Methods

Chlorophyll Fluorescence Dark-adapted fluorescent measurements (Fv/Fm)

measured with a LI-COR 6400XT Portable Photosynthesis and Fluorescence System day following each disinfectant spray application four and seven days following final spray application

Common Visual Injuries to Camellia Foliage• Necrotic lesions on leaf tips • Necrotic lesions on leaf

margins• Necrotic foliage spotting

Oxidant

<3-6% MTR(not damaged)

>3-6% MTR(damaged)

Rate (ppm) Visual Analysis No. Rate (ppm) Visual Analysis No.

Chlorine Dioxide 0 7 0

Chlorine Dioxide 0 + SARC 7 0 + SARC

Chlorine Dioxide 100 7 100

Chlorine Dioxide 200 6 200 7

Chlorine Dioxide 400 3 400 4

Chlorine Dioxide 100 + SARC 6 100 + SARC 7

Chlorine Dioxide 200 + SARC 4 200 + SARC 5

Chlorine Dioxide 400 + SARC 3 400 + SARC 4

Hydrogen Dioxide 100 7 100

Hydrogen Dioxide 100 + SARC 7 100 + SARC

Threshold of Marketability

Conclusions

Changes in camellia foliage chlorophyll fluorescence (Fv/Fm) in response to oxidant applications occurs three days earlier than visual symptoms

Electro-BioCide applied at a rate predicted to eradicate Phytophthora ramorum (200 mg·L-1) will not visually damage plants until after five consecutive spray applications

Conclusions

Sarcosinate surfactant increases Fv/Fm with increasing oxidant concentration

Electro-BioCide has a positive effect on photosynthetic functioning over time

Contact Information

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• Website:http://www.greenhouse.colostate.edu

• eMail:[email protected]