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PSA

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  1. PSA Understandinghow Coppers Work TIM TORREASTPACK

  2. How does Copper work • Protective bactericides • Must be applied before significant bacterial innoculum arrives. • Not systemic – no re-distribution will occur post application. • Require moisture to be present on plant surface to be active. • Copper particles gradually desintegrate releaseing Cu+ and Cu++ ions. • Cu++ ions are absorbed by bacteria and destroy the enzyme system in the pathogens. • Copper is most effective on those diseases that need free water present to develop Tim Torr

  3. How does Copper work • Cu+ and Cu++ ionsare pathogen killers in water on the leaf - Leaf surfaces are wetter than the atmosphere, this is the “boundary layer effect”. - Plants excrete acids on to leaf surface. - pH below 6.5-7.0 is required to produce Cu++ and Cu+ ions • Too rapid release of these ions causes plant damage! Tim Torr

  4. Leaf chemistry pH 5-7 Tim Torr

  5. Leaf chemistry pH 5-7 Tim Torr

  6. Bactericidal effect I Tim Torr

  7. Bactericidal effect II Tim Torr

  8. Bactericidal effect III Tim Torr

  9. Copper Bactericides There are five basic types of Copper compounds • Copper oxychloride • Copper hydroxide (Kocide , Champ etc…) • Tribasic copper sulphate (Green and Blue Coppers) • Copper ammonium complexes (dark blue liquids, e.g. Liquicop) • Cuprous oxide (Red coppers, e.g. Nordox) Tim Torr

  10. Copper Bactericides • They have different characteristics. • Important characteristics are • Solubility and • Particle size Tim Torr

  11. Solubility Soluble Coppers • Erode faster and require more frequent applications In-Soluble Coppers • Release a lasting supply of Cu++ and Cu+ ions in the acidic environment of the plant surface • Require less frequent re-application Tim Torr

  12. Solubility Cuprous oxide Oxychlorides Hydroxides Copper sulphate Least soluble Most soluble Solubility is a factor of • Particle size • Temperature and moisture • Form and formulation Tim Torr

  13. Particle Size • The smaller the particle size the greater the number of particles per gram of copper applied. • This dramatically improves the coverage of the product on the plant. • The smaller the particle size the greater the surface area per gram of copper applied. • This means that there is far more surface area available to react and release Cu++ and Cu+ ions Tim Torr

  14. The effect of small particle size on coverage

  15. Particle Size • Smaller particle size gives greater retention of the product on the plant surface because there is a greater proportion of the particle in direct contact with the plant surface relative to their weight. • Copper product particle retention is influenced by • Rainfall, direct dislodgement or solubilisation by the water present. • Wind events, can dislodge the larger particles. • Rubbing against other parts of the plant Tim Torr

  16. Loss of Copper product from the leaf surface of Gold kiwifruit leaves during a simulated rainfall event. • The remaining product is becoming more persistent as the larger particles disappear. Tim Torr

  17. Cupric hydroxide Cu(OH)2 - Crystal structure - 2.5 microns av. Tim Torr

  18. Cuprous oxide Cu2O (Nordox) - Fine cubes - less than 1.0 microns av Tim Torr

  19. Copper Phytotoxicity • Too many Copper ions at any one time can cause damage to the plant. • Darkening of the leaf veins • Dead spots on the leaves • Marking on the Fruit • Thickening of the leaf cuticle • Loss of vigor of shoots Tim Torr

  20. Tim Torr

  21. Tim Torr

  22. Copper Phytotoxicity Can be caused by anything that results in a large number of Copper ions being absorbed by the plant… • Slow drying conditions • pH of spraying solution is too low (below 6.5) • Form of Copper is too soluble e.g. Copper sulphate • Product rate is too high • Impurities in the sprayed product e.g. heavy metal contaminants or chlorides Tim Torr

  23. Summary Coppers • Are not systemic • Release copper ions on the plant surface • Copper ions are the real “active ingredient” • Coppers need to be applied before the bacteria arrives • Can be very persistent on the plant surface • Small particle size is more effective • Small particle size is more persistent • Insoluble Copper formulations last longer • Need to be applied in good drying conditions Tim Torr

  24. Any Questions ? Tim Torr