I live in La Selva Beach CA (near Santa Cruz) and have 4 Shin deshojo maples with what my landscape contractor believes to be powdery mildew. I have tried two different fungicides but the new red growth continues to be blighted and to die. The trees leafed out nicely but now the trees are slowly defoliating. I have the Vertrees book, which I have read and am concerned that the trees are untreatable. The trees are about 5 feet tall and are planted in the ground in openings in my brick patio. The openings are about 18 inches square. The trees grow almost entirely in the shade except for early mornings. I have other japanese maples growing successfully on my property but not in patio openings (numerous bloodgoods, oshio beni, harpstring, several sangos, seriyus). What can or should I do?