How to control Cytospora Canker. Planning a New Orchard. Prune your infected cherry tree during the growing season when it’s easier to identify the cankers. Control of Cytospora canker requires that all diseased branches be cut back to the nearest living laterals or to the trunk of affected trees. Fungicides are not very effective against the Cytospora canker, so prevention is key to controlling the disease. Cytospora or Leucostoma canker is one of the most damaging diseases of Colorado blue spruce, Picea pungens, in the landscape. CHESTNUT "BLIGHT" is a trunk canker caused by the fungus Endothia parasitica. Plant tree species that are resistant to the fungus. The bark should not be injured unnecessarily, since the fungus may enter through wounds resulting from injuries. Botryosphaeria Canker. Managing Cytospora canker involves total orchard management. Management. Select a site well away from old cytospora-infected trees. CHESTNUT (Castanea) -- chestnut "blight", Cytospora canker, decay, Endothia canker, leafspot, shoestring rootrot, shothole leafspot, twig canker, Verticillium wilt. Treatment: There is no chemical control for Cytospora canker. Management. There are no universally registered chemicals for the treatment of cankers. Colorado blue spruce trees are no longer recommended for planting in Maryland. Since no stone fruit tree is immune and fungicide treatments alone are not effective, control efforts must be aimed at reducing tree injuries where infection could begin. Other susceptible spruces include black, Norway, Oriental, and white. Control infection by limiting tree stress. Season: Cytospora canker thrives in the summer when temperatures are above 90 degrees. Fungi in Botryosphaeria genus are typically opportunistic pathogens; they will attack trees that are stressed due to biotic and abiotic conditions. Botryosphaeria species are known causal organisms for dieback and cankers in most trees and shrubs. Cytospora canker is a warm-season (summer) disease with peak fungal growth occurring just above 90 o F. Canker growth potential is highest when temperatures are high and prune tree growth activity is low (July-September). Tree Canker Treatment. There is no known chemical control for Cytospora. Cytospora canker is most common on trees over fifteen years old, but may occur on younger trees as well. Due to climate change, summers are too hot and humid as well as too warm in the winter. The Cytospora canker doesn't attack healthy undamaged bark, so prevent mechanical injuries to roots, trunk and limbs and reduce insect damage.