The aster bushes at our park have gotten some mildew (I think). It starts at the base and works its way upward, but the plant still blooms and is beautiful at the crown. Any input to help will be greatly appreciated.
Certified GKH Gardening Expert
Treat the plant with a fungicide. We like neem oil, which is both an organic pesticide and fungicide. Here is more info: https://www.gardeningknowhow.com/plant-problems/pests/pesticides/neem-oil-uses.htm