Agriculture Reference
In-Depth Information
Copper
Copper acts against both fungal and bacterial pathogens and is particularly
effective against bacteria. Different formulations are available. Copper
sulfate is blended with sulfur in Bordeaux mix to provide a highly effective
fungicidal and bactericidal treatment.
Fixed copper compounds include tribasic copper sulfate, copper oxychlor-
ide sulfate, and cupric hydroxide. These materials are effective in disease
control and are easier to prepare and safer to apply during the growing sea-
son than Bordeaux mix. Unlike Bordeaux mix, they do not stain plant sur-
faces, which can be important in ornamental landscapes and orchards. Take
care when using copper-containing materials in your orchard. Copper is a
heavy metal and persists in soils. Confine your spray materials only to the
aboveground portions of plants and follow label directions carefully.
Bordeaux Mix
Bordeaux mix is one of the most valuable sprays for organic orchards, com-
bining copper and sulfur. The downsides are that it is sticky, is corrosive
to metal, stains plant surfaces and clothing, and stinks. On the plus side, it
is highly effective in controlling many trunk, cane, foliar, and fruit diseases.
Bordeaux holds up well on the trunks and canes during winter rain and snow,
providing long-term protection. It is usually applied between leaf fall and
new spring growth. The following information was derived, in part, from in-
formation published by the University of California Integrated Pest Manage-
ment program.
Many different Bordeaux mixture formulations are available. One of the
easiest and best all-around formulations uses a 10:10:100 blend of copper
sulfate (not fixed copper), dry hydrated lime, and water. Hydrated lime (a
powdered material used to make plaster) and copper sulfate are readily
available at garden centers. Use powdered copper sulfate and keep the cop-
per sulfate and hydrated lime dry during storage. When they absorb mois-
ture and become lumpy, they are hard to work with. Buy fresh hydrated lime
