Japanese magnolias (Magnolia x soulangiana), also referred to as saucer magnolias, add beauty to your home garden that is easily disrupted by fungus problems. A variety of fungi attack Japanese magnolias, utilizing them as host plants and creating cosmetic to severe health damage. Provide optimal care to avoid fungus problems on the Japanese magnolias in your home landscape.
Healthy Japanese magnolias have a greater chance of resisting or recovering from fungus problems than neglected or weakened trees. Grow Japanese magnolias in locations that provide full sun for proper development, according to the University of Florida IFAS Extension. Japanese magnolias thrive in moist, porous, well-drained soil high in nutrients.
Verticillium wilt is a fungus problem that attacks Japanese magnolias. Caused by the fungal pathogens Verticillium albo-atrum and Verticillium dahliae, fungi inhabit soil and invade through plant roots, preferring flowering trees and stressed root systems, according to the University of Illinois Extension. Gray mold is another fungus that attacks Japanese magnolia trees, caused by fungal pathogens from the Botrytis species. This fungus spreads sporadically on wind and water, landing and germinating on the wet plant tissue of uninfected plants.
Verticillium wilt of Japanese magnolias results in yellowed, wilted leaves that often curl and eventually die and drop from the tree. Look for branch dieback and, underground, roots often decay. In magnolias, vascular discoloration often causes a green hue to appear in sapwood, according to the University of Illinois Extension. Depending on the infection, your plant may recover, decline slowly or die quickly. Gray mold in Japanese magnolia results in lesions on buds, flowers, stems and leaves as well as a gray, mold-like substance on affected areas. Gummosis, or the gummy rot of plant parts, often occurs. This disease generally causes diminished overall health and severe cosmetic damage.
There are no resistant plants to gray mold. However, avoid highly susceptible plants to lower risk of repeat infection. Highly susceptible plants include, but are not limited to, white fir, kousa dogwood, eastern larch and Norway spruce. Fortunately, there are plants resistant or immune to verticillium wilt including, but not limited to, apple, beech, fir, mulberry and willow trees, according to the University of Minnesota Extension. Reducing likely hosts aids in keeping your gardening space free of fungus infection.
There are no known effective chemical controls for gray mold. Though fungicides may offer minimal assistance for verticillium wilt, they are not highly effective. Contact a licensed professional or your local county extension agent if you feel chemical assistance is your final option. For natural control, keep your Japanese magnolias vigorous and free from injury through which pathogens invade. Avoid overhead irrigation that creates standing water on foliage, offering a prime environment for fungi germination. Additionally, avoid waterlogged soil. Remove and destroy infected plant parts to control disease spread. Always sanitize pruning tools between each cut and from one tree to the next to inhibit transfer of fungus.