Weeping cherry problem
Plant has been in the ground three years and has grown well. This year, yellow leaves and leaves with holes appeared and leaves fell to ground. Tree has been sprayed twice with Sevin (no bugs noticed on leaves or underside) and twice with Fung-onil (fungicide). All sprayings have been at recommended dilutions. Leaves continue to fall. Photographs of tree and close up of leaves attached.
We viewed your photos. The foliage looks like it was subject to cherry shot hole, a fungal disease. This can be common when we have wet spring weather and may continue to infect leaves throughout the growing season if rainy weather persists. In most cases trees recover from these diseases and no treatment is necessary.
Remove and dispose of fallen leaves in the fall to reduce overwintering pathogens.
Be sure to identify the pest or disease before you decide to spray. Sevin is a broad spectrum insecticide that affects many beneficial insects, and is not effective on this disease.