Oleanders are actually very easy-care plants that grow and thrive lushly 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 pots in this country. However, this attitude promotes a whole range of different diseases, as potted oleanders are often weakened due to incorrect or lack of care and are therefore more susceptible to pathogens and pests.
What diseases and pests occur in oleander and how to treat them?
Common diseases affecting oleanders include oleander canker, dry rot and gray mold. Oleander cancer can be treated by pruning, dry rot and gray mold can be treated by pruning and fungicidal sprays. Pests such as aphids, spider mites and mealybugs and mealybugs can be controlled with pesticides.
Common diseases and how to treat them
Some diseases - mostly caused by bacteria or fungi - are very common in oleander. In many cases, you bring the pathogens into your home when you buy a new oleander bush, which is why it makes sense to initially isolate the new addition - this will prevent a wave of infection from spreading to other plants. Diseases introduced in this way become noticeable very quickly and, the sooner you recognize and combat them, you can get them under control quite well. As a preventive measure, you can only ensure that you care for the oleanders as carefully as possible and give them a warm, sunny location without drafts. Preventive spraying, for example with fungicides, is also possible, which is usually carried out in autumn. However, many oleanders react very sensitively to fungicidal pesticides.
| Illness | Symptoms | Treatment |
|---|---|---|
| Oleander crab (Pseudomonas) |
|
Strong pruning measures in case of infestation, return to he althy wood. No effective pesticides available for home gardens. |
| Dry rot (Ascochyta) |
|
Radical pruning into he althy wood, preventative measures with fungicidal sprays possible. |
| Grey mold (Botrytis) |
|
Inject fungicidal agents, remove fallen flowers, prefer self-cleaning oleander varieties. |
| Sooty mildew (Oidium) |
|
Wipe with water or diluted vinegar solution for stubborn infestations, combat lice. |
Oleander crab (Pseudomonas)
Oleander cancer, 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 turn black and – in the case of infected buds – burst.
- Stunted buds don't open at all.
- Cauliflower-like growths appear on the shoots.
- Infected shoots can snap or break off.
- Brown spots appear on the leaves or the leaves turn brown.
- The brown spots eventually burst open and the leaf bends.
Control is only possible with strong pruning measures, in which you cut affected parts of the plant back to the he althy wood. Unfortunately, there are no effective pesticides approved for home gardens. In addition, the disease will most likely recur once it has broken out - the bacteria are in the plant and cannot be removed.
Dry rot (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 initially affected, and they dry up and fall off. As the disease progresses, the symptoms also appear in the shoots and from there travel to the roots. Once the roots are affected, the oleander can usually no longer be saved. In this case, too, control is only possible by radically cutting back deep into the he althy wood. Act as quickly as possible to prevent the fungus from reaching the base. However, preventive measures with fungicidal sprays are possible to prevent infection from occurring in the first place. The corresponding products are best sprayed in autumn. 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.
Grey mold (Botrytis)
The gray mold caused by the Botrytis fungus only affects the flowers of the oleander, preferably the varieties with double flowers. The disease occurs primarily in winter quarters, but also in humid and warm summers.at high humidity. As a preventative measure, you can inject fungicidal agents or pick off the oleander flowers before putting them away for winter quarters. Even in rainy summers, it can make sense to remove dead flowers and thus eliminate risk factors. When buying, give preference to self-cleaning oleander varieties, as these are generally significantly less sensitive to gray mold than others.
Sooty mildew (Oidium)
Sooty mildew, also known as star sooty mildew or black spot disease, manifests itself as a black coating on the leaves of the oleander. This disease is the result of an infestation by aphids or scale insects, whose sugary excretions (honeydew) provide an ideal basis for the colonization of black fungus. This coating restricts photosynthesis because it clogs the pores on the leaf surfaces. Sooty mildew can usually be washed off with water; if the infestation is stubborn, a diluted vinegar solution can help. However, the focus should be on combating the lice that make sooty mildew possible.
Common Pests and How to Treat Them
Especially during the winter months, there is often an infestation with various plant sap-sucking pest insects. Due to the less than optimal conditions during the cold season, oleander is particularly susceptible to spider mites etc. For this reason, it is important to check the plants regularly and intervene in a timely manner - the sooner you notice an infestation and take action, the faster the annoying creatures will disappear.
Aphids
These stubborn pests can only be found on the soft shoots of the oleander, but primarily on the inflorescences and new shoots. The sticky excretions of the aphids are particularly problematic because these can promote fungal infestation (particularly with sooty fungi). Aphids can be sprayed 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 discover, because as soon as the typical fine webs can be seen with the naked eye, they have already spread significantly. Spider mites can be treated very well - even as a preventative measure - with plant protection products based on rapeseed oil.
mealybugs and mealybugs
These plant lice, which are also very common, can also be easily combated with products based on rapeseed oil; alternatively, regular wiping with a soft soap solution also helps.
Tip
When the oleander drops its buds, a lack of light - for example as a result of a period of bad weather - is often the cause.
