Apply a protectant fungicide such as chlorothalonil, Bordeaux mixture or choose from several copper fungicides that are labeled. Spray in the spring before bud break to protect the older needles and a second time in the mid summer to protect the new needles. The first application is to protect older needles. The second application protects the new growth. This disease is typically not as damaging as needle diseases on spruce, but it can cause substantial losses if left uncontrolled.
Control is very successful on ornamental plantings following two years of fungicide applications.
This bacterial disease is carried from tree to tree by insects. The cankers on infected trees will soon begin oozing a milky to amber-colored exudate that contains the bacteria. This sticky material attracts insects that carry the bacteria to other trees. The bacteria enter the host through the blossoms, leaves or wounds. Since most apples are now in bloom, this disease may cause numerous blossom infections this year.