A:     Copper is a common ingredient used in spraying dormant trees for plant diseases like peach leaf curl, various blights, and bacterial infections such as canker.

If you see signs of disease and wish to control it with a dormant spray, be certain that your tree is truly dormant. There should be no sign of new buds or beneficial insects that could be harmed by the copper or smothered by the sometimes oily sprays.

The optimum time is generally December through February. Of course, with an early onset of warm weather and early budding, all bets are off.

Read the labels on copper sprays. Look for at least 50% copper in the ingredient list. Less may be ineffective. If your chosen spray is a Bordeaux mixture, it is good for only one year and should not be stored longer.

The best way to control bacterial, viral and fungal diseases is to avoid them. Keep weeds down with a layer of organic mulch that does not touch the tree’s trunk, and make sure there is good drainage.

For additional information request a free copy of Leaf Curl Pest Note 7426 and Bordeaux Pest Note 7481 by contacting the SLO Master Gardeners.