Leaf spot is a common term that is applied to a number of diseases that affect the foliage of your trees. The majority of these will be some kind of fungi, but some can be caused by a type of bacteria. Some insects are also able to cause damage to the foliage of a tree, which will look the same as leaf spot disease. This is a common issue and often does not require any spraying, though it may not look good. Contact a certified arborist if you have questions or concerns about your diseased tree.
Symptoms and Diagnosis of Leaf Spot Disease
The main symptom that you will see with leaf spot disease are spots that come on the foliage. These spots will vary in size and color depending on the plant that is affected, the organism that is involved, and the stage of development.
When you look at the leaves on your trees, you may notice a brownish spot, which can sometimes be tan or black. Concentric rings or dark margins will show up. The fungi that show up will be with block dots too. These spots can combine to form a larger blotch on the leaf as well.
The Life Cycle
Any organism that causes leaf spots will survive in infected leaves and twigs that fall. Some will remain inside the dead twigs that are on your tree. Most damage will happen in the spring so you are more likely to see this at that time. When the weather gets wet, the spores can splash or be windblown over to other leaves, which will then get infected. Wet periods make it more likely that this disease will happen.
How to Treat Leaf Spot Disease?
There are a few different options that you can utilize to help manage leaf spot disease. Some of these include:
- Live with the disease: Most of the trees available will do fine with these leaf spots with no damage. If the tree is affected early enough in the year, it will just re-leaf and the new ones will not be infected. Only if defoliation happens for at least three years in a row will some negative effects happen.
- Remove the infected leaves: You may also want to remove any leaves that have been infected. Raking them up and then disposing of them will help make it so the disease will not spread over time.
- Keep the foliage dry: You do not want to use overhead watering. A soaker hose or watering early in the day allows the foliage time to dry before night and can prevent the spread of disease.
- Keep the plants healthy: Since your plants will often be able to handle a bit of this disease without defoliation, keep the plants in good health to help them rebound quickly.
- Use fungicides when needed: If the infection gets really bad, you may want to do a fungicide to help. These can prevent the spread of the infection and can help to keep the tree safe. Sprays will not be able to cure the infected leaves though so the damage may already be done by the time you can spray.
- Replace the plant: If the infection just shows up on a small plant, then you may want to get rid of it and try again. For a large tree, this is harder, but since it will often be fine with a little of the infection, you do not need to do much for this.