He althy magnolias are quite resistant to pest infestation and other diseases. A disease should therefore always be seen as a symptom that your magnolia is weakened and therefore vulnerable due to an unsuitable location or incorrect care. The following diseases in particular are common in weakened magnolias.
What diseases are typical of magnolias?
Common diseases of magnolias include leaf spot and powdery mildew. Leaf spot appears as black spots and holes on the leaves, while powdery mildew appears as a whitish or grayish coating. Pest infestation by whiteflies, scale insects or root damage is also possible, especially on weakened plants.
Leaf spot disease
The leaf spot disease is caused by Pseudomonas bacteria, which mainly live in raindrops or rainwater. It occurs mainly in warm but humid weather and is characterized by black spots surrounded by a yellowish halo or even holes on the leaves. As a result, affected shoots die. This very widespread plant disease is also a problem with deciduous magnolia species because the bacteria overwinter in the shoots and often cause frost damage.
Fighting leaf spot disease
The best way to combat leaf spot is through prevention: It is important that the crown of the magnolia is not too dense, but allows enough light and air to enter. The leaves should always be able to dry quickly, which is why you should never water from above in summer (especially not with rainwater), but only directly at the roots. In the event of an infestation, the affected plant parts must be removed as quickly as possible.
Mildew
There are two different types of powdery mildew, both of which initially appear as a whitish or grayish coating on the leaves. Later the leaves turn brown and fall off. This plant disease is caused by Erysiphaceae fungi.
Prevent and combat mildew
Mildew can be combated very well with a garlic decoction or lactic acid. For the latter, mix one part whole milk with nine parts water and spray the magnolia over a period of several days. If there is a severe infestation, only fungicides often help (€11.00 on Amazon). Infected shoots and leaves should be removed immediately as mildew spreads very quickly.
Pest Infestation
Weakened magnolias are often attacked by whiteflies or scale insects, whose excretions cause fungal diseases (e.g. B. with the sooty mold fungus) and promotes an infestation with aphids. The roots, on the other hand, can be eaten by larvae or caterpillars that live underground and thus damage the tree. Voles and black weevil larvae in particular like to feast on the juicy magnolia roots.
Tips & Tricks
Prevention is better than cure, so you can help endangered magnolias to quickly get rid of annoying pests with a special fungicide fertilizer. By the way, dried coffee grounds are also said to help.
