Leaf spot (lat. Septoria)
Septoria is manifested by brown spots on the leaves (lighter in the center, darker at the edges). Completely infected leaves and shoots die. The shrub should be treated with copper sulfate or another copper-containing spray to combat typical fungal diseases.
More about this:Effectively combat leaf spot disease on hydrangeas
Ring spot disease caused by Mycosphaerella brassicicola
Bark spot disease is caused by the fungus Mycosphaerella brassicicola. Infection occurs most commonly at 16-20°C during wet periods and is particularly common in cabbage plants. Small spots 3 to 5 mm in diameter appear on the leaves and can grow up to 2 to 3 cm in size. They are initially green-brown, then turn gray when dry and black when wet. A ring of chlorosis forms at the outer edge and a nectoric tissue develops within the lesion. Fungicides with the active ingredient azoxystrobin from the chemical group of ß-methoxyacrylates (strobilurin derivatives) are suitable for combating ring spot disease.
Insects that transmit hydrangea diseases
Hydrangea diseases are often transmitted to healthy plants by pests. These insects include:
- Gall nematodes
- Spider mites
- Dickmaulrüssler
- Scale insects
- Aphids
The use of insecticides from the group of neonicotinoids, such as the active ingredient imidacloprid, is recommended against pests. The avermectins are also a common component of insecticides and acaricides, such as Vertimec pro.
Preventative measures to protect your hydrangeas
Since diseases develop under certain weather conditions, the risk of infection in constant rain in summer is quite high. Preventive measures to protect plants are therefore extremely necessary:
- In autumn and early spring, the bushes should be treated with a copper spray against fungal diseases.
- Before you plant new plants in your garden, you should also treat the soil with a copper-containing pesticide.
- Old, fallen leaves and plant remains should be carefully collected.
Moderate watering, proper soil selection, and regular fertilization are essential ingredients for proper hydrangea care. If you provide your hydrangeas with ideal growing conditions and take preventive measures, they will thank you with magnificent flowers. The diseases and pests shown in the photos are not so serious if the necessary measures are taken in a timely manner. Is your hydrangea not blooming? Here are8 reasons for missing flowers.
