Gray Mold [Trees and Shrubs]

Botrytis often lives on dead plant material and from there, spread into weakened living plant material. It can also infect through wounds or healthy tissue without going though dead or dying tissue. This fungus disease can cause twig blights on stems, buds, flowers, fruit and leaves; can be confused with other diseases that cause similar damage. It can cause gummosis, fruit rot and damping off. When humidity is high a thin to thick web of mycelium develops on diseased tissue. This mycelium is grayish in color, hence the name gray mold. Symptoms may vary depending on the plants attacked, plant parts attacked, and growing conditions. Botrytis is sometimes confused with old age and thrips damage. To help separate browning on petals caused by old age versus botrytis, check the petals closely. Browning from old age should occur on the outer petals first and along the edges or at the tip of the petals. When inner petals or the middle of the petals develop brown lesions first, gray mold is probably the reason. On leaves that are relatively thin such as redbud, lesions are light brown to brown and irregular. On fleshier leaves such as rhododendrons, concentric rings of different shades of brown may be visible.