Not only petunias, but also many other plants in the garden can sometimes have a quickly spreading, white coating. Since this is a fungal disease that is extremely damaging to plant health, appropriate preventive and control measures should be taken as part of petunia care.
White coating on petunias is almost always powdery mildew
Location and care for low-susceptibility petunias
Petunias originally come from natural distribution areas in South America and thrive particularly well in warm, sunny locations. However, uncovered locations in the garden can pose problems for the popular balcony plant due to the often regular rainfall in this country. If lush hanging petunias are very close together, they have difficulty drying after rainfall, which promotes some fungal diseases. In addition, powdery mildew and downy mildew can spread particularly easily in the garden or on the entire balcony if the plants are very close together, since the fungal spores then only have to travel short distances.
The downy mildew
Downy mildew can be distinguished from powdery mildew in that the white coating on the plants can mainly be observed on the undersides of the leaves. At the same time, yellow and brown spots appear on the upper side of the leaves until the leaves finally wither completely. Downy mildew occurs mainly when there is too much moisture, which can become a problem in rainy summers and in less sheltered locations for the petunia. With any type of powdery mildew, small infested areas should be cut out and removed as early as possible so that further spread can be stopped or at least contained. Regular checks are necessary for this, even if they spend the winter indoors.
The Powdery Mildew
In the case of powdery mildew, the fungus, which is visible as a white coating, mainly spreads on the upper side of the petunia leaves, but also affects all other parts of the plant. Powdery mildew is favored by the alternation of wet periods and dry phases. It can therefore be prevented by cultivating the petunias indoors and watering them sufficiently during dry periods. The following applies to the treatment of both types of powdery mildew:
- Cut out affected areas if possible
- dispose of the removed material with household waste if possible
- spray the plants with a broth made from horsetail
Spraying the affected areas with a mixture of 9 parts water and 1 part commercial milk also helps.
tips
The white coating of powdery mildew is not only a problem for petunias, the dangerous fungus can also spread to other plants in the garden such as cucumbers, salsify and dahlias.