In the Orchard
There are two times to spray for peach leaf curl in the Sacramento area: in early December after the leaves have fallen off, and again in February. The February spray should be applied at bud swell just before the buds begin to open, but before pink bud stage. See the pictures below. When the flower buds begin opening, there is risk that the spray may damage the fruit.
Because January has been warm and dry, bud swell is likely to occur earlier this year and the time to spray may be a week or two earlier than usual.
See detailed information from UC IPM Online about managing peach leaf curl, including suggested fungicides to use. Note that this information suggests adding 1% horticultural spray oil to the mix for copper ammonium products, but doesn't specify the amount of oil to add. This works out to 2.5 tablespoons (or 1.25 oz.) per gallon of water.
Four bloom stages of peaches and nectarines
|Dormant bud||Bud swell||Pink bud||Full bloom|
Master Gardeners at the Fair Oaks Horticulture Center sprayed different products on the peach trees in the demonstration orchard during 2012 to see how well they prevented peach leaf curl. See results of the demonstration.