Leaf disease(s) of evergreens
Hello, I have six garden plants that have similar diseases. In some cases these are serious and I need to take urgent action. I have attached photos of the first three and will follow this with a 2nd email with the second three They are:
1. Photinia. spots all over leaf surface, they expand and ultimately the leaf falls at the end of the season. Most leaves on the bushes. These are old, large, semi-trees.
2. Prunus laurocerasus # 1. Holes in leaves with dead leaf covering hole. Approx 10% of two old large bushes.
3. Prunus laurocerasus # 2. There are 5 bushes, seriously affected, planted 2 yrs ago. The edge of the upper half of the leaves are dead and fall off in a strip. There is no damage to the rest of the leaves. All leaves yellower than the Prunus laurocerasus #1 bushes (above). There are small, healthy-looking buds, but no new growth, unlike others of the same species that have already flowered.
I am sending the second set of pictures now.
What you are seeing on your broad-leaved evergreens are a combination of leaf spot diseases and cold damage, also called winterburn.
It is not the same disease on every plant. The organisms are somewhat plant- specific and generally are not of great concern.
As spring continues, a new flush of growth will cover these tired leaves and they will fall. In most cases leaf spotting diseases will not threaten the health of the shrub.
Cultural control consists of raking beneath the shrubs and disposing of the diseased leaves to limit the amount of pathogen in the garden. Selective pruning to improve airflow (and sunlight from trees above) so that leaves can dry off more quickly can help.
For you Photinia, they are commonly affected with a fungal leaf spot in our area.
We don't recommend the plant for this reason. Here is a page about that:
Cherry laurels commonly get leafspot diseases. Management is same as above.
Your third photo shows the winterburn. Broadleaved evergreens can dry out in the winter climate, and it shows up in the leaves.
More about this, including tips to avoid it here: http://extension.umd.edu/hgic/winter-damage-trees-and-shrubs