My customer has a 30 year old giant sequoia growing in less than favorable conditions. The canopy is somewhat lank in appearance and has brown areas. The tree is rather crowded and shaded by other trees to the north. The soil is about 12" powdery clay over hardpan (consolidated clay with rocks). Fungi Phytophthora and Rhizoctonia were cultured from an adjacent Daphne. The customer prefers to not use fungicides such as Subdue. He is willing to apply mycchoriza producing fungi. Other ideas? The tree has sentimental value. The location is Medina WA, a waterfront suburb of Seattle. Thank you!