Identifying and Treating Magnolia Tree Diseases

Many magnolia diseases can be controlled with basic precautionary measures and timely disease management. There are more than 200 kinds of magnolias and majority of them are vulnerable to a variety of leaf diseases. Among these, leaf spot and leaf blight are the two most common.

Magnolia Leaf Blight

Leaf blight is a common garden disease caused by a fungus. In some plants, it doesn't cause widespread damage, but it can be extremely damaging to young magnolias.

Leaf Blight Symptoms

The first symptoms include the appearance of thread-like formation on the underside of leaves. Once the blight spreads, the leaves develop a defining, matted appearance. These leaves tend to stick together, creating a clustered appearance. Due to the heavy threading in many blight-affected magnolias, this disease is also called Fungal Thread Disease.

Leaf Blight Control

You should prune-off all affected branches. Even if a few leaves appear to be blighted on a branch, prune-away the entire branch. Don’t use these branches for composting. You should burn them immediately and even the residue shouldn’t be used for any gardening activity. Before pruning, ensure that your pruning tools have been dipped in an industrial fungicidal preparation. This helps to ensure that the infection is not spread through the pruning equipment.

Magnolia Leaf Spots

Leaf spots in Magnolias are caused by a variety of fungi. Among these, the most common fungi include the Cladosporium and the Septoria. They are associated with magnolia spotting in household gardens. The Pseudomonas bacteria can also cause magnolia leaf spotting, but its occurrence is rare.

Leaf Spot Symptoms

Gardens in perennially wet conditions or those exposed to heavy irrigation are more prone to being attacked by leaf-spotting organisms. The initial symptoms include development of tiny, black or purplish spots. The mature spots have a white-colored center and their outer edge is dark purple. Spotting that has been present for more than five months often gives rise to fruiting bodies that appear near the spotted leaves.

Leaf Spot Control

You should not use overhead irrigation. This is known to be a common cause for creating excessively moist conditions along the upper foliage. Prune-away any kind of weathered vegetation and sort-out young, intertwining branches. This helps to control spotting by reducing contact with diseased foliage and increasing ventilation. You can make magnolias immune to spotting diseases by spraying them with fungicides during their early development. Use multi-dimensional fungicides for this purpose. Start spraying magnolias with such fungicides soon after transplanting them in the garden soil.

Magnolia Disease Caused by Insects

The Neolecanium or the Magnolia Scale is the most destructive of magnolia pests. These insects grow within the thick foliage spread of magnolias without displaying any signs of their early development. Once the crawlers emerge, they feed intensively on the young buds. Magnolias attacked by scale are known to become ready victims for a typical kind of fungal infection. The Black Mold fungus spreads quickly through foliage that has been destroyed by the feeding scale.

Magnolia Scale Symptoms

Magnolia scales can hollow-out young branches. The slender stems start bending and often die. Leaves appear under-developed and those infected by Black Mold develop a typical black, sooty appearance.

Magnolia Scale Control

Pruned branches sold at garden supply stores are often the carriers of dormant scale infection. Check the magnolia branches you plan to use for growing purposes in your garden. If the tree shows signs of scale feeding, using horticultural oils is recommended. These are available at pest control stores. Magnolia stems should be repeatedly sprayed with a mixture of soap, water and the horticultural oil.