Valued for their large, beautiful flowers along with the dense shade they supply, magnolia trees (Magnolia spp.) Are generally healthy and trouble-free. The few pest insects that feed on magnolia trees cause little harm, but you do need to be on the lookout for a few diseases. The over 250 species of magnolia trees vary in hardiness. If you reside in U.S. Department of Agriculture plant hardiness zones 5 to 10, you will discover a lot of species and cultivars that grow and bloom reliably in your area.
Honeydew and Sooty Mold
Several little, sucking insects secrete a sticky substance called honeydew since they feed. Honeydew is usually accompanied by the dark sooty mold fungus. Honeydew and sooty may be the very first signs you notice since the insects as well as their feeding damage are hard to see up in the branches of a magnolia tree. Aphids, mealybugs and scale insects will be the prime suspects. These insects have lots of natural enemies that usually maintain the residents in check. If therapy becomes necessary, use narrow-range horticultural oil sprays in early spring while the insects are young and haven’t yet developed protective coverings.
Feeding Damage to Leaves and Flowers
Caterpillars sometimes feed on magnolia leaves, leaving them looking muddy and tattered. Magnolia trees can easily withstand light feeding, but severe infestations may require treatment. Spray with Bacillus thuringiensis while the larvae are young. Hoplia beetles are 1/4-inch long insects that feed on white magnolia blossoms. The very small beetles and the little, round holes they leave in the blossoms are hard to see in tall magnolia trees. Since the feeding only lasts two to four weeks and the insects are difficult to control with insecticides, it is ideal to simply wait out the infestation.
Spotted and Scorched Leaves
Leaf scorch and leaf spot cause discolored, spotted, scorched-looking leaves. Sprays are ineffective against those disorders. The most appropriate plan of action would be to get rid of influenced plant if the tree is small enough that you can do this safely, and clean up fallen debris and leaves promptly to prevent the spread of infection. Powdery mildew makes the leaf appear like it’s been sprinkled with talcum powder. Moderate to severe cases may require treatment with a fungicide. Sulfur sprays and horticultural oils are great choices, but never use them within two weeks of one another.
Blight and Husband Back
Blight and die back are brought on by a bacterial infection. The symptoms are shriveling and blackening leaves and twigs. In severe cases you may see cankers and brownish streaks in the branches. Sprays are ineffective, so pruning is the best solution for treatment. Prune off influenced stems several inches below the damage. Disinfect pruning shears with disinfectant spray, alcohol or diluted household bleach between cuts to prevent spreading the illness. Don’t fertilize the tree as you’re treating for blight and dieback. Fertilizers that contain nitrogen may encourage the disease.
Cankers, Rot and Mushrooms
Cankers are sunken places in the wood of a magnolia tree. They usually include dead wood and may be surrounded by thickened or calloused tissue. If the damage isn’t extensive, it is ideal to leave them alone. Don’t attempt to carve out the dead wood or fill in the holes. Trees that are rotting on the interior may show no signs until mushrooms or fungus begin growing on the trunk and branches. There isn’t any remedy for this condition. Trees with extensive cankers or decay present a potential danger to homes and property because of the risk they may fall. Have the trees assessed by a professional arborist, and have the tree removed if it’s a danger.