Lime sulphur and dormant oil are some safe insecticides to use on fruit trees. Apply lime sulphur and dormant oil with a pump sprayer and coat the trunk and branches. These supplies are available at most plant nursery stores.
Make sure the tree is dormant, or not in bloom, before applying. Otherwise, you could kill the tree and harm beneficial insects, including bees, that pollinate fruit trees.
Make your own dormant oil by mixing 1 cup of vegetable oil with 2 tablespoons of dish soap in 1 gallon of water. Mix the oil and soap first, and then add the water. Shake the mixture often while applying.