Transcript INCREASING PRODUCTIVITY

PSA
Understanding how
Coppers Work
TIM TORR
EASTPACK
How does Copper work
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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
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How does Copper work
• Cu+ and Cu++ ions are 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!
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Leaf chemistry pH 5-7
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Leaf chemistry pH 5-7
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Bactericidal effect I
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Bactericidal effect II
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Bactericidal effect III
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Copper Bactericides
There are five basic types of Copper compounds
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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)
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Copper Bactericides
• They have different characteristics.
• Important characteristics are
– Solubility
and
– Particle size
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Solubility
Soluble Coppers
• Erode faster and require more frequent applications
In-Soluble Coppers
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Release a lasting supply of Cu++ and Cu+ ions in the
acidic environment of the plant surface
Require less frequent re-application
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Solubility
Cuprous oxide
Oxychlorides
Least soluble
Hydroxides
Copper sulphate
Most soluble
Solubility is a factor of
- Particle size
- Temperature and moisture
- Form and formulation
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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
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The effect of small particle size on coverage
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
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• 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.
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Cupric hydroxide Cu(OH)2
- Crystal structure
- 2.5 microns av.
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Cuprous oxide Cu2O (Nordox)
- Fine cubes
- less than 1.0 microns av
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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
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Copper Phytotoxicity
Can be caused by anything that results in a large number of
Copper ions being absorbed by the plant…
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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
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Summary
Coppers
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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
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•Any Questions ?
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