Below is a summary of copper formulations, their characteristics, and their limitations.
Copper Fungicides
· Fixed Copper
o
Safer
for plant tissue than “bluestone” copper (see below)
o
May
be used throughout growing season, but may cause fruit russetting
o
Low
solubility in water, lower risk for phytotoxicity
o
Release
copper ions slowly (with water/rain), longer residual
o
Slow
drying time (rainy conditions) increases solubility, ion release, and phytotoxicity
o
Acidic
conditions/additives increase solubility, ion release, and phytotoxicity
§ Adjuvants, phosphorus acid
fungicides, and mancozeb lower pH
o
Use
high rates during dormancy for fire blight management (until ½” green)
o
Lower
rates during growing season for management of other diseases, may add lime
o
Common
forms of fixed copper fungicides
§ Basic copper sulfate – Cuprofix,
Basicop, Phyton, Agristar
§ Copper Hydroxide – Kocide, Champ, Badge, NuCop, CuPro
§ Copper oxychloride sulfate – C-O-C-S
§ Cuprous oxide – Nordox, ChemCopp
· Copper sulfate pentahydrate – bluestone
o
Dormant
spray, only
o
CuSO4.5H2O
o
Highly
soluble ions, phytotoxic
o
Often
combined with lime to help tie up copper ions
o
No
residual activity, rapid release of copper ions
o
Common
brands of copper sulfate
§ Mastercop, Magna Bon, Aquavet, Delcup
Tree fruit diseases managed with copper fungicides:
- Fire blight (spray guide recommendations: dormant – label: silver tip to green tip)
- Apple scab (dormant to pink)
- Bacterial canker (after harvest and late dormant)
- Bacterial spot (dormant/budswell, pink, and petal fall)
- Peach leaf curl (dormant)
- Cherry leaf spot (after petal fall)
- Black knot (dormant)
Large numbers of copper ions (rapid release of ions) are phytotoxic to plant tissue, especially leaf tissue
Copper fungicides are not systemic and wash off with rain. Fixed coppers have more residual activity due to slow release of copper ions.
Metallic copper equivalent is the amount of copper available for fungicidal activity (different from active ingredient). Basic copper sulfate usually contains the highest metallic copper equivalent.
Copper can accumulate in soils, inhibit plant growth, and is toxic to microorganisms and earthworms
More on fire blight at http://nicolewarduk.blogspot.com/2013/04/fire-blight-infections-occur-during.html
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