Another approach is to use a water-soluble fertilizer once a week, being careful never to apply more than the recommended rate. Container plants are easily burned or killed by too much fertilizer. You can be extra safe and provide even more consistent fertilization by applying half doses twice a week. The leaves of some of our shade trees are marred by irregular blotches. Yvonne Carree, University of Idaho extension forestry associate, suspects anthracnose, a fungal disease that frequently affects shade trees and deciduous shrubs.
Symptoms usually begin at the edges of leaves and move inward along the veins.
Plants can also have twig and stem cankers. Spores of the anthracnose fungus overwinter in cankers on the tree and on fallen leaf litter and nuts. They're spread by wind, rain and irrigation systems and are particularly prone to flourishing after warm, wet springs. To substantially decrease spore numbers, you'll want to rake up leaves and nuts and either burn them or remove them from your property. Also adjust your sprinklers so water doesn't hit the foliage.