Presentation delivered as part of the Colorado State University Research Updates at the ProGreenEXPO in Denver, CO 12 February 2014.

1. ASSESSMENT OF DISINFECTANTS FOR CONTROL OF
PHYTOPHTHORA RAMORUM

2. 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 EXPO
11 February 2014

3. Assessment of disinfectants for control
of Phytophthora ramorum
• Collaborative project between:
– CSU Agricultural Experiment Station
– USDA-APHIS Center for Plant Health Science and
Technology

5. 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

7. 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.

8. 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.

9. 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.

10. From:
Scott Pfister, Director
Forest Pest Programs
USDA APHIS PPQ

11. From:
Scott Pfister, Director
Forest Pest Programs
USDA APHIS PPQ

12. Disinfection
Common industrial oxidizers and their potential relative to chlorine
Oxidant
Oxidation 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

13. Disinfection
Pathogen survival from laboratory simulations and
hydrocooler studies according to Suslow (2003)
Survival at ORP (mV)
Pathogen
< 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

14. 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/PHP2008-0922-01-RS.

15. Heather Hammack’s
MS Thesis Research

16. 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.

17. 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)

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

19. 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

21. Methods
Visual assessments:
 Three days after each of the five successive spray
applications
 Six and 14 days following the final spray
application

22. 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

25. Common Visual Injuries to
Camellia Foliage
• Necrotic lesions on leaf tips
• Necrotic lesions on leaf
margins
• Necrotic foliage spotting

28. Threshold of Marketability
<3-6% MTR
(not damaged)
Oxidant
>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

29. 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

30. Conclusions
 Sarcosinate surfactant increases Fv/Fm with
increasing oxidant concentration
 Electro-BioCide has a positive effect on
photosynthetic functioning over time

31. Contact Information
• Review and share this presentation:
http://www.slideshare.net/snewman7118
• Website:
http://www.greenhouse.colostate.edu
• eMail:
Steven.Newman@Colostate.edu