One of the most attractive shrubs in the garden is undoubtedly the rhododendron. With its large pink, purple or white flowers, it will beautify and attract attention. But even these azalea-like plants of the heath family are not immune to various diseases.
Rodendrons are native to mountainous regions such as the Himalayas. Some of the diseases are mainly due to the fact that our climatic conditions do not always suit them completely.
Diseases affecting leaves
Plants often suffer from loss of dye in or to their leaves, which is usually caused by unsuitable soil conditions. The soil may be waterlogged or have an unsuitable pH factor.
Most common diseases that are visible on the leaves:
- Chlorosis – manifested by minor light spots and loss of pigment throughout the leaf over time. The cause is the aforementioned high alkalinity of the soil. The pH value should be kept between 4,5 and 5,5. If the soil is too alkaline and contains a higher calcium level, the plant will lack iron. This is the main cause of chlorosis.
- Leaf spot – Leaves have yellow to black spots that get larger over time. One cause may be sunburn or frost. However, it is the fungal disease that causes the symptoms described. The plant suffers from this if the bush is waterlogged. If there is old, unsaturated water under the bush, drain it away.
- Fall – The disease develops initially on the underside of the leaves, then spreads to other parts of the plant. Fallen leaves are easy to spot, they look like white dust or flour and can be wiped off. The fungus overwinters in the soil and in spring spreads by wind to infect other plants. Keep a close eye on the plant, remove the infested parts immediately and burn them, do not overdo it with nitrogen. If the infestation is extensive, use fungicides.
Pests of Rhododendrons
Unfortunately, in addition to disease, insect pests also attack shrubs. Very often the leaves are nibbled by the larvae of various insects, but the adults will also eat the leaves. These can be, for example, rhododendron whitefly or aphids. Some pests also carry pathogenic spores of fungal diseases. Consult experts for advice on the suitability of spraying.