Two fungicides used to control debilitating peach leaf curl in peach and nectarine trees have been taken off the market. To prevent this disease, gardeners can make their own fungicide by following the directions in UC Pest Note 7481, Bordeaux Mixture. The process requires buying a small quantity of copper sulfate and agricultural lime to make a stock solution of each chemical. Combine them and dilute with water to make the Bordeaux spray, which is applied twice while the trees are dormant. Lime by the pound can be purchased at City Farmers Nursery; copper sulfate is available from Amazon.com. For more on peach leaf curl, consult UC Pest Note 7426, Peach Leaf Curl.