Oleanders are actually very easy-care plants that grow and thrive in their warm home regions without any special measures. However, since the shrubs are not sufficiently hardy in our country, they are preferably cultivated in tubs in this country. However, this attitude favors a whole range of different diseases, since tub oleanders are often weakened due to incorrect or lack of care and are therefore more susceptible to pathogens and pests.
Lice like to eat oleanders
Common diseases and how to treat them
Some diseases - mostly caused by bacteria or fungi - are very common in oleanders. In many cases, you bring the pathogens into the house when you buy a new oleander bush, which is why it makes sense to keep the new addition isolated at first - this will prevent a wave of infection from spreading to other plants. Such imported diseases become noticeable very quickly and, the sooner you recognize and fight them, you can get them under control quite well. As a preventive measure, you can only take care of the oleanders as conscientiously as possible and give them a warm and sunny location without drafts. In addition, preventive spraying with fungicides, for example, is possible, which is usually carried out in autumn. However, many oleanders are very sensitive to fungicidal pesticides.
Oleander crab (Pseudomonas)
Oleander canker, caused by Pseudomonas bacteria, is one of the most common diseases. Basically, almost all oleanders are already infected with the pathogens, although the disease does not always break out. The following characteristics are typical:
- The first symptoms usually appear on the flowers or buds.
- Flowers and buds wither and cannot develop properly.
- Instead, they thicken, often turning black and - in the case of infected buds - bursting.
- Crippled buds don't open at all.
- Cauliflower-like growths appear on the shoots.
- Affected shoots can snap or break off.
- Brown spots appear on the leaves or the leaves are turning brown.
- Eventually the brown spots will burst open and the sheet will curl.
Control is only possible with strong pruning measures, in which you cut back affected parts of the plant far into the healthy wood. Unfortunately, there are no effective pesticides that are approved for the home garden. Also, once the disease breaks out, it will most likely keep coming back - the bacteria are stuck in the plant and cannot be removed.
Blight (Ascochyta)
Dry rot is caused by fungi and usually occurs as a result of overwintering or after a rainy summer. Here, too, the flowers are affected first, which dry up and fall off. As the disease progresses, the symptoms also appear on the shoots and migrate from there to the roots. Once the roots are affected, the oleander can usually no longer be saved. In this case, too, control is only possible with a radical pruning far into the healthy wood. Act as quickly as possible to prevent the fungus from making its way to the base. However, preventive measures with fungicidal sprays are possible here so that an infection does not take place in the first place. The appropriate funds are best sprayed in the fall. By the way: To minimize the likelihood of infection, oleanders should never be cut in autumn - the resulting wounds are ideal entry points for fungi and other pathogens.
Gray mold (Botrytis)
The gray mold caused by the Botrytis fungus only affects the flowers of the oleander, preferring the varieties with double flowers. The disease occurs primarily in the winter quarters, but also in damp and warm summers or when the air humidity is high. As a preventive measure, you can inject fungicides or pluck the oleander blossoms before putting them away in the winter quarters. Even in rainy summers, it can make sense to remove faded flowers and thus eliminate risk factors. When buying, give preference to self-cleaning oleander varieties, as these are usually much less sensitive to gray mold than others.
Common pests and how to treat them
Especially during the winter months, there is often an infestation with various plant sap-sucking insects. Due to the less than ideal conditions during the cold season, oleander is particularly susceptible to spider mites and the like. For this reason, it is important to check the plants regularly and to intervene in good time - the earlier you notice an infestation and take countermeasures, the faster the annoying little creatures will disappear again .
aphids
These stubborn pests can only be found on the soft shoots of the oleander, but mainly on the inflorescences and the new shoots. The sticky excretions of the aphids are a problem for you, because these can promote fungal infestation (especially sooty fungi). Aphids can be hosed off with a sharp jet of water, for example in the shower. The treatment should be repeated several times.
spider mites
These tiny little animals are very difficult to spot, because as soon as the typical fine webs can be seen with the naked eye, they have already spread considerably. Spider mites can be treated very well - also preventively - with plant protection products based on rapeseed oil.
Mealybugs and mealybugs
These plant lice, which are also very common, can also be effectively combated with rapeseed oil-based products. Alternatively, regular wiping with a soft soap solution also helps.
tips
When the oleander sheds its buds, the reason is often a lack of light - for example as a result of a period of bad weather.