Lightly infected leaves of Modesto ash may not fall. Twigs are also infected. Fungus spores spread in splashing rainwater. Prune out and destroy infected twigs and branches, since they provide a source of inoculum during the following spring. Apply fungicide before budbreak in spring.
Thorough coverage is important.
If rain occurs within 24 hours of application, reapply treatment. Fertilize and provide deep irrigation during summer. Leaves turn brown around the edges, and sometimes between the veins. Results from lack of water balance in the tree, or xylem plugging by bacterium. Brought on by hot, drying winds, drought, shallow soils, inadequate irrigation, etc.