Dormant spraying is an effective & relatively safe way to prevent many of the insect & disease problems that plague our gardens. It’s called dormant spraying because it applied to deciduous plants when they are dormant & leafless.
There are two types of dormant sprays. Liquid copper (copper ammonium complex or copper octanoate) is an effective fungicide & bactericide. Horticultual oil smothers overwintering insects & insect eggs. Copper & oil can be combined & applied at the same time.
Peach leaf curl is best controlled with a dormant spray. Unfortunately, the two most effective sprays, tribasic copper sulfate (microcop) & lime sulfur (polysul) are no longer available. Use copper ammonium complex (Monterey Liquicop) with at least 1% horticultural oil. I use 4T Liquicop + 5T Volck oil per gallon of water. I have not found copper octanoate to be effective. I spray 3 times (Thanksgiving, New Years, Valentine’s Day) for trees prone to leaf curl. Keep in mind that plums do not get peach leaf curl (leaf curl on plums is caused by aphids). Trees need to be sprayed before they break dormancy.
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