Greenhouse disinfectant research


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Presented during the CSU Research Updates session at the 2013 ProGreen EXPO in Denver Colorado

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  • The fluorescent data was analyzed separately from the foliar data, because of four leaf samples per plant did not match with the dataset containing the single plant data for the foliar growth and morphology data. In general, the fluorescent results differed, or only slightly mirrored the results from the plant growth and leaf morphology analysis. The Fv/Fm results show that all five study factors had a significant effect on plant fluorescence. Also, there were six significant two-way interactions among the study factors, not including soil temperature. Finally, there were three significant, two-way interactions between soil temperature and the study factors. In general, Fv/Fm measurements increased as the time of measurement increased from 8 to 16 days after treatment or CFF inoculation. In other words, the plants appear to be resisting the wilt bacteria over time, or showing less biotic stress symptoms over time. Fv/Fm increased from 0.81 to 0.82 for the control and Electrobiocide + surfactant treatments when measured at 8 and 16 days, respectively. A comparison between the oxidant treatments and the control plants show that plants were less wilt stressed, i.e. had higher Fv/Fm values, for some oxidant treatments when compared to the control. The complexity describing each of the six two-way interactions in a simple summary is difficult at best, and may be misleading at worse. A full description of all the interactions will be described in journal article written for this study.  The results for the leaf area, foliar biomass, and relative growth rate analysis for the fourth study reveal a somewhat different set of interactions between the three study variables. In general, there was one significant two way interaction (inoculation date * inoculation status) for the analysis for total leaf area, fresh and oven dry above ground biomass, SLA, and relative growth rate. Each of the study factors (chemical treatment, inoculation date, and inoculation status) had a slightly different plant growth response, but the overall study factor effects tended to mirror each other. The Relative Growth Rate (RGR) response reveals that the inoculation date or whether the plants were inoculated with CFF before or after the chemical treatments had a significant effect on the plant growth. Plants that were treated with the oxidants four days before being inoculated exhibited better overall growth. In addition, plants that were inoculated with CFF wilt had decreased growth when compared to non-inoculated plants. Finally, four out of the five chemical treatments had no effect on RGR, but chlorine dioxide + sarc did reduce RGR when compared to the four other treatments. Overall, the results show that oxidant disinfectants sprayed before the plants were inoculated resulted in better plant growth. Also, the inoculated plants did have slower growth than the non-inoculated plants. Finally, the oxidant disinfectants show some promise for improving natural plant defenses against foliar injury from the bacterial wilt. This study only had six replications among the treatments, which was not enough to lower the variation between treatments. Future studies should focus on the most effective treatments and increase the number of plant replications in order to reduce variation between treatments
  • Greenhouse disinfectant research

    2. 2. Colorado State University Research Updates Assessment of disinfectants for control of Phytophthora ramorumSteven E Newman, Ph.D., M.S. Greenhouse Crops Extension Specialist and Professor of Floriculture ProGreen EXPO 17 January 2013
    3. 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
    4. 4. Team• Steven E. Newman – co-principal investigator• Craig Ramsey – co-principal investigator• Heather Hammack – MS horticulture student• Debra Newman – research associate
    5. 5. 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.
    6. 6. 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.
    7. 7. 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.
    8. 8. From:Scott Pfister, DirectorForest Pest ProgramsUSDA APHIS PPQ
    9. 9. From:Scott Pfister, DirectorForest Pest ProgramsUSDA APHIS PPQ
    10. 10. Oxidation ReductionOxidation is defined as an increasein the positive oxidation numberwith a corresponding loss ofelectronsReduction is a decrease inthe positive number of ionswith a corresponding gain inelectrons
    11. 11. Common industrial oxidizers and their potential relative to chlorine Oxidation potential Oxidation relativeOxidant (mV) to chlorineFluorine 3,050 2.25Ozone 2,070 1.52Hydrogen peroxide 1,780 1.31Potassium permanganate 1,680 1.25Chlorine dioxide 1,570 1.15Chlorine 1,360 1.00Bromine 1,070 0.70
    12. 12. Water solutions of sodium hypochlorite and its impact onoxidation reduction potential and pH Oxidation potential NaOCl (%) (mV) pH Water 210 6.8 0.3 715 8.9 0.5 690 9.6 1.0 655 10.1 1.5 630 10.6 2.0 599 11.2 3.0 570 11.7
    13. 13. Pathogen survival from laboratory simulations and hydrocooler studies according to Suslow (2003) Survival at ORP (mV)Pathogen < 485 550<X<620 >665E. coli O157:H7 > 300 s < 60 s < 10 sSalmonella spp. > 300 s > 300 s < 20 sL. monocytogenes > 300 s > 300 s < 20 sThermotolerant coliform > 48 hr > 48 hr < 30 s
    14. 14. Sources Chlorine reaction in waterChlorine gas Cl2 + H2O 4 HCl + HOClSodium hypochlorite NaOCl + H2O 4 NaOH + HOClCalcium hypochlorite Ca(OCl)2 + 2 H2O 4 Ca(OH)2 + 2 HOClChlorine dioxide HOCl+HCl+2NaClO2 4 2ClO2+2NaCl+H2O
    15. 15. Sodium Hypochlorite Chemical Injectors
    16. 16. Hypochlorate Metering Pumps
    17. 17. Calcium Hypochlorite High volume systemTabletreservoir HOCl concentrate
    18. 18. Calcium Hypochlorite Medium volume system Water Storage Tablet feeder
    19. 19. Chlorine Dioxide Gas pure membraneSodiumchloritefrom storage 25x more active + than chlorate Cell Water No trihalomethanes Water Pump Weak caustic Control - soda system
    20. 20. 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.
    21. 21. Contact Information• Review and share this presentation:• Website:• eMail: