In the Mediterranean area and in almost all warm regions of the world, oleanders are everywhere and grow wild. The abundance of flowers and the sheer size of the plants are impressive. Unfortunately, in our Central European climate, these plants can only be cultivated as container plants. They don’t tolerate frost. When it comes to care, this hibernation is the tricky point. During this time, diseases and pests often spread to the oleander. If they are not recognized or recognized too late, they can cause major damage. The same also applies to pesticides. Oleanders sometimes react very badly to these. Read the text below to see what needs to be taken into account.

Characteristics

  • Oleander – also called rose laurel
  • Dogbane family – all parts are poisonous, including the sap
  • Homeland – Mediterranean area and Orient
  • Evergreen woody plant
  • Can grow up to 3 m high
  • Oblong, leathery, dark green leaves
  • Flowering from June to September
  • Multiple flowers in umbellate inflorescences
  • Flower colors – white, ivory, yellowish, apricot, salmon, as well as various shades of pink to violet
  • Simple and filled varieties
  • Numerous varieties with a floral scent

Control pests and diseases

Actually, oleanders are very robust plants. They grow wild in many countries and do not require any care. Even if they stand as a hedge on roads and highways, they usually have to do without any maintenance. Nevertheless, the plants thrive and bloom reliably every year. In the bucket, however, they are not quite as easy to care for. Mistakes in care lead to the weakening of the otherwise very robust plants and make them vulnerable. Diseases and pests can spread to the oleander. This must be prevented, or they must be recognized in good time. The earlier you intervene, the easier it is to succeed. Once the pathogens and pests have really multiplied, it becomes difficult. In addition, oleanders sometimes react very badly to insecticides and sprays used to control diseases.

diseases in oleanders

There are some typical diseases that occur in oleanders. No matter how well the plants are cared for, there is not much that can be done preventively against bacteria and fungi, apart from good care. Diseases are often brought in when you buy something. Pesticides ensure that the oleander plants look healthy. But the diseases are already on or in the plant. They become visible very quickly.

Oleanderkrebs – Pseudomonas

Oleander canker is caused by bacteria. These are located directly in the plant and move in the sap stream. Almost all oleanders worldwide carry these bacteria. The symptoms are often only visible on individual shoots. Growths can be seen on the shoots, but also on the leaves and inflorescences.

  • Flowers and buds show the first symptoms.
  • Inflorescences wither as they develop
  • Thickenings appear, they turn black and the buds burst
  • Either only stunted flowers open or they don’t open at all
  • Only stunted seed pods are formed
  • Shoots burst open lengthwise
  • Cauliflower-like growths become visible
  • In the case of large growths, the shoot can snap off at this point
  • The leaves show brown spots that get bigger and bigger and finally burst open
  • The leaf bends, the midrib bursts open

Control
There are no means that are approved for home gardens. You have to live with the disease and make the best of it. There are a few measures to get the oleander disease under control. You cannot completely wipe them out because the bacterium is in the plant.

  • Oleander canker can only be combated by radical pruning measures.
  • A weak infestation with the oleander canker is not so bad. Many varieties of oleander can cope with the disease and reliably sprout again even after a cut.
  • Never dispose of pruning waste in the compost, as this will spread the disease further.
  • In the case of severe infestation, cut back the affected shoots down to the healthy wood.
Note: When pruning, it is imperative to use sanitized tools to avoid spreading more disease to the already weakened plant. Even after the cut, the tools must be thoroughly disinfected. The tools are the main carriers of the disease.

Blight—Ascochyta

Dry rot is a fungal disease that usually occurs during overwintering. All above-ground parts of the plant are affected, especially the soft ones. The oleander often dies as a result. Usually the inflorescences are attacked, which appear to be drying up. They die off and the dry zones move on, simply along the shoot, always towards the base.

  • Shoots without flowers can also be affected.
  • You can see one or more brown spots on the shoot.
  • The shoot overlying the spots is lost and dies.
  • If the fungus reaches the base, the entire plant is threatened and often cannot be saved.

The fungus spreads through spores, which in turn spread through water. The spores enter through injuries. Minor wounds also occur when a leaf or inflorescence falls off. Soft tissue is particularly susceptible to the fungi. If the disease usually also occurs in the winter quarters, it can also become a problem outdoors in rainy summers. The fungal spores are spread with the rain and run down the plant. Plants that are very densely overgrown and where the moisture stays inside are particularly susceptible.

combat

Here, too, only a radical cut will help. The affected shoot or shoots must be cut out. The cut must go into the healthy wood. It is important to prevent the fungus from fighting its way to the base. Everything above the affected area is lost and must be cut off. Dispose of the shoots in the household waste or burn them. Never put it in the compost.

  • You can also do something to prevent or keep healthy, so that the plants strengthened in this way can better defend themselves against the infestation.
  • Regular spraying with fungicides, but at least before putting them away in autumn
  • It is important that the plants are sprayed until dripping wet. The agent must run down the shoots.
  • Coat the base of the oleander with a fungicide, which is also used in fruit growing. The white or brown coating that develops depending on the agent cannot be penetrated by the fungi. So the oleander is protected at the most important point.
  • After cutting, seal the cuts down to the healthy wood with a fungicide-containing tree wax.
  • If possible, do not cut in autumn, as the fungus spreads particularly well in the winter quarters. The wounds are ideal entry points.
Tip: It is best to choose oleander plants with a heavily woody base. These especially have plants grown from cuttings.

Grauschimmel

Gray mold is also a fungal disease. Compared to the two diseases mentioned above, however, gray mold is relatively harmless. This fungus occurs mainly in double-flowered oleander species and also preferably in the winter quarters. Gray mold only occurs on the inflorescence, on dried flowers that were not removed when they were put away. Mold often occurs during longer periods of rain in summer and when the air humidity is high. All inflorescences of a plant can be affected and die off.

combat

  • Regularly remove the faded and dried flowers from the inflorescence.
  • Clean the entire plant before putting it away in the fall.
  • Self-cleaning oleander varieties have no problems with gray rot and should be preferred
  • Spraying with antifungal agents is also helpful

Pests on oleanders

Pests like to attack the oleander plants during the winter. During the darker months of the year, conditions in the roost are often less than ideal and this weakens the plants. Pests exploit this mercilessly. Here it is important to regularly check for an infestation. Timely discovery and intervention usually prevents worse.

What pests are there?

  • Aphids – do not stop at oleanders, but are relatively easy to combat. Aphids suck plant sap and transmit diseases to the oleander.
  • Spider mites – like to infest oleanders that are particularly protected and those indoors, especially during the winter. They suck on the plants and weaken them massively. Spider mites are the most dangerous pests for oleanders.
  • Mealybugs – quite rare pests, but not to be underestimated. Over time, they multiply and can cause major damage. They suck plant sap.
  • Scale insects – well camouflaged and shielded pests that are often overlooked at first. Occur both outdoors and indoors. They also suck plant sap.

spider mites

Spider mites are very common. In addition, they are also very difficult to detect. A little trick helps. The fresh shoots, shoot ends, buds and blossoms are sprayed with the water spray bottle. If small, very fine webs appear, they are usually caused by spider mites. If you can see the webs with the naked eye, i.e. without the fine water droplets that make the nets visible, then the pests have already multiplied and spread a lot. Then it is high time to intervene. In addition, the pests can be identified on the leaf itself, by the light and white speckles along the central panicle. Most spider mites are on the underside of leaves. After some time, the entire leaf appears silvery.

Fight

  • Put plants in the wind in summer. Where there is air movement, there are fewer spider mites.
  • It also makes sense to increase the humidity. If the infestation is severe, this is usually pointless.
  • In most cases you cannot do without chemical aids.
  • With regular use, rapeseed oil-based products help, but 3 applications a year are necessary for them to help. The sprays cover the pests with a film under which they suffocate because there is no air to breathe. It is important to wet all parts. Don’t do it in the sun!
  • It is ideal to spray in spring when exhibiting and in autumn when exhibiting. Should spider mites appear in the meantime, treat again. Repeat after 10 days to catch the young just hatched from the eggs.

scale insects

Scale insects are brown to black, oval spots about 3 mm in size on the shoots and leaves, mostly on the underside. The lice camouflage themselves so well that they are usually not even noticed. What is striking are their excretions. The sticky substance that falls on the ground around the plant or on underlying leaves is called honeydew. In summer, when the plants are outside, you can also see a lot of ants on the oleander, nibbling on the sap. Honeydew is also dangerous, as sooty mold fungi grow on it over time. These also weaken the oleander and can be recognized by the black coating.

Fight

  • Remove lice one at a time with a toothpick or skewer and a rag soaked in soft soap. This is time-consuming work and usually you don’t catch everyone.
  • Alternatively, the oleander can be sprayed with a soft soap solution. In this way, the pests are detached from the surface and can then simply be hosed off with a sharp jet of water. The lye needs to soak in a bit.
  • Alternatively, the agents against spider mites based on rapeseed oil are suitable.
  • Here, too, only chemistry usually helps. Systemic agents help, but many oleanders do not tolerate them well.
  • With the systemic means, the plant absorbs the poison. The pest stings them and sucks out the sap that contains the poison. That’s deadly.

Mealybug

Mealybugs can be recognized by the white, cotton-like small and larger dots on the leaves, shoots, shoots and in the root area. Small dots are individual insects, larger ones are mostly nests. They consist of a whitish wax coating, the excretions. Mealybugs suck plant sap.

Fight

  • Same measures as for scale insects

aphids

Aphids stop at almost no plant, including oleander. They occur outdoors and indoors and can be found on new shoots and inflorescences. They only settle on the soft parts of the oleander, they don’t stand a chance on the hard ones. Their tools are too weak for that. Sucking is less damaging, although it can transmit diseases to the oleander. Far more damaging are the excretions. The sticky sap attracts ants, who literally herd and milk aphids. Sooty mold fungi are promoted and leaf discoloration, shoot and flower anomalies occur.

Fight

  • The easiest way is to hose off the lice with a sharp jet of water. The treatment usually has to be repeated several times.
  • Insecticides also help. The lice die. After a few days, remove the sticky honeydew with a jet of water.
  • Plant protection sticks help preventively. They are systemic agents that are absorbed by the plant. With large plants, however, it is a question of cost, because many of the sticks are required and they are quite expensive.
  • Beneficial insects are a good alternative. They eat aphids. In the field, however, the purchase makes little sense. A greenhouse, in which the container plant is kept for a while, is more suitable, provided it is not full of healthy plants.
  • Ladybugs can be lured into the garden with, for example, dill, chamomile, corn poppy, yarrow and buckwheat.

Frequently Asked Questions

What can you do to prevent diseases and pests on oleanders?
Both diseases and pests usually only appear on weakened plants. It is therefore important to take good care of the plants. Healthy plants defend themselves and usually cope well with such influences. Weakened plants are vulnerable. They are weakened by care mistakes. It is important to avoid this.

Does cool hibernation help to keep pests from spreading?
Yes something. At 0 to 10°C and plenty of light, the plants do well and pests will not be able to spread as much, because they like it warmer. However, they are usually not killed. However, warm hibernation creates significantly more problems.

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