Chemical Treatment for Leaf Spot – Copper-based fungicides may help control bacterial leaf spot if applied in late spring. Fungicides containing chlorothalonil and
Two types of fungal diseases can infect hydrangeas — cercospora leaf spot and anthracnose. Cercospora leaf spot (Cercospora hydrangea) begins as brown or purple spots on the leaves at or near the base of the plant. The circular spots are often small and scattered and usually measure 1/8 to 1/4 inches in diameter. Spots on the bigleaf hydrangea develop tan or gray centers surrounded by brown or purple halos. Leaves may eventually turn yellow-green and fall off. Anthracnose is caused by the fungus Colletotrichum gloeosporioides. It produces large brown spots on leaves that eventually develop lighter brown or tan centers. The spots may also appear on blossoms and may appear angular if bordering a vein. Bacterial leaf spot in hydrangeas is caused by the pathogen Xanthomonas campestris and affects primarily Hydrangeae quercifolia, Hydrangeae arboreacens and Hydrangeae macrophylla. Like cercospora leaf spot, the disease first manifests itself on the lower leaves of the plant in the form of purple to reddish spots. As with anthracnose, spots bordering veins become angular.
Magnolia Frescati – Below is from here.
Leaf Spot Diseases
Leaf spot diseases are caused by varying strains of fungi. Leaf spot diseases cause brown or yellow irregular discolorations on the foliage of magnolia trees. In severe cases, these discolored leaves may fall from the branches prematurely. Generally, leaf spot diseases can be tolerated if the magnolia tree is healthy.
Leaf discoloration and distortion, cankers, wilting, stem dieback and premature leaf dropping are a few of the common symptoms of bacterial blight. Regularly pruning during dry seasons will help provide good airflow between the branches. Chemical control is generally not recommended and is not a reliable method
Verticillium wilt appears as yellowing on the leaf margins and between veins of magnolia leaves. The infected leaves wilt, die and prematurely fall from the magnolia. This fungal disease begins at the tops of leaves and works its way back toward the tree branches. Verticillium wilt is not present in cool temperatures; the first signs of the fungal disease won’t be visible until the weather warms. There is no acceptable fungicide control to treat verticillium wilt. However, cultural control will help prevent this damaging fungal disease from attacking the magnolia. Planting magnolia trees in disease-free soil greatly reduces the chance of verticillium wilt. You can sterilize the soil before planting with solarization to kill pathogens living in the top several inches of the soil.
Powdery mildew is a contagious fungal disease that infects plants such as magnolia trees. Powdery mildew appears as a powdery or fuzzy white growth on leaves and branches. This fungus causes the tree’s foliage to discolor, wilt and fall off the branches. Shade and mild temperatures between 60 and 80 degrees promote powdery mildew growth and — unlike
When the magnolia is infested with pests — such as aphids, spider mites