Camellia Leaf Damage
I have two camellia plants that were planted early last summer. Within the last two weeks the leaves have gone from a healthy shiny green to a damaged brownish green. Both plants have extensive damage. Some leave are partially green but have small circles where the color has changed. These camellias are a more cold hardy variety. What is causing this sudden leaf damage?
Washtenaw County Michigan
Appears to be algal camellia leaf spot, possible scale damage as well, but culturing in the lab might prove otherwise. Camellias, cold hardy or not, are seldom grown in Michigan to my knowledge. In fact, I don't believe I've ever seen one growing here. To do so requires a mindset of providing optimum growth conditions for the plant, the first being to give it protection from drying cold winter winds. Has there been a soil test performed on the growing soil? http://msusoiltest.com/ Like rhodos and azaleas, camellias need acidic soil. Soil pH can change over time, especially with concrete sidewalks, driveways or building foundations nearby that can leach lime to the soil, increasing alkalinity. Watering is another is another potential issue. The plant should be deeply watered going into winter to maintain hydration. My point is that less than optimal growing conditions allows for attack by disease and/or insects because the plant will be less effective in it's ability to defend itself. Cold hardy maybe but cold is likely another factor here, especially being the plant's first winter. You are growing plants that will always require extra attention.
MSU's Diagnostic Services is very good at diagnosing plant problems and I would send a plant sample to them, for a small fee. Once diagnosed, they would also make recommendations as to how to treat or care for the plant going forward. Check out the link: https://pestid.msu.edu/
Otherwise here are two links to more camellia info: