- Numerous fungal diseases cause spots to appear on the leaves of trees, including diseases of the genera Alternaria, Ciborinia, Coccomyces, Hendersonia, Marssonina, Venturia and among others, according to the University of Illinois Extension. Although leaf spot diseases may not cause serious problems for the tree if they appear later in the growing season, spots forming in the early spring or summer lead to deformed leaves, weak growth and the potential for the death of the tree in severe cases.
- Apply fungicides to the tree and the soil around the affected area to kill the fungal spores and stop them from spreading. Remove fallen leaves, twigs, flowers or fruit from around the base of the affected tree and other trees, as these become spore hosts for the fungi. Apply fungicides according to the directions on the package and repeat sprays as needed to control any further outbreaks of the problem.
- Some diseases causing leaf spots are the result a bacterial problem. Fire blight is a serious bacterial disease affecting apple, pear and a number of other tree species. The disease causes spots on the leaves, kills branches and flowers, may kill the tree. Many bacterial diseases are spread via insects or through the soil. Treating bacterial diseases is crucial.
- The best way to treat bacterial diseases causing leaf spots is prevention. Keep the trees free of pests as much as possible, dig channels around the base of the tree to get rid of standing water and keep the tree's growing environment healthy. Remove affected portions of the tree as soon as they are noticed. Use a copper fungicide for moderate control of some bacteria, including fire blight.
Fungal Diseases
Fungal Disease Treatment
Bacterial Diseases
Cultural and Chemical Control
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