Oleander with its delicate flowers and shiny foliage is an ornament for every garden - but also quite sensitive to various pests and diseases. These tend to occur towards the end of winter, as the lack of light weakens the plant and makes it vulnerable. On overwintered oleanders, for example, gray leaves can often be observed, which can have various causes.
Gray leaves are often an indication of pest infestation
Gray, stunted leaves indicate spider mites
Stunted leaves with a grayish-white coating are often the result of pest infestations, most commonly spider mites. As soon as the leaves look like this, the infestation is already very advanced - they have been damaged by the sucking behavior of the insects and will no longer regenerate. Remove the foliage and shower the oleander with a strong jet of water. Repeat this procedure over and over again and also place the plant in a draftier location - spider mites love warmth and dryness, which is why they are very sensitive to regular showers and an airy place. In addition to spider mites, pests such as red spiders or thrips also cause the damage described.
Fungal diseases often possible cause
The oleander is also extremely sensitive to various fungal infections. In many cases, gray leaves are therefore also the result of an infestation with powdery mildew or gray rot (grey mould).
mildew
Experts use the term “mildew” to summarize two different clinical pictures. The so-called powdery mildew causes a clinical picture with leaves covered with a mealy, grey-white coating. This disease, which is quite common in oleanders, is mainly caused by excessive humidity. The host fungus withdraws valuable nutrients from the plant, so that growth comes to a standstill and the oleander only produces a few flowers. A treatment with a milk-water mixture (whole milk and water in a ratio of 1:10) is helpful, which you spread generously over the affected parts of the plant using a spray bottle. Repeat the process several times at intervals of a few days and weeks.
Gray mold (Botrytis)
Gray mold occurs primarily on oleanders with double flowers, while varieties with single flowers are hardly ever affected. To prevent this, you should pluck the faded flowers before putting them into winter quarters and thus deprive the fungus of any food source - it first settles on the flowers.
tips
In order to avoid infestation with pests or fungi, you should put the oleander in its winter quarters as late as possible and clear it out again as early as possible.