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White spots forming on the leaves of an oleander plant usually indicate disease or pest infestation. I had these spots show up on my oleander recently. Understanding the cause is the key to addressing this so I did a lot of research and this is what I’ve learned.
Getting rid of white spots on oleander plants can be done by removing the scale insect, which is the main cause of the white spots on the plant. The insects can be eliminated by regular pruning or by spraying it with insecticides or horticultural oils.
I’m going to do my best to provide you with the information that I’ve learned about what those white spots really are, how you can get rid of them, and tips to prevent them from coming back.
What Are White Spots On An Oleander Plant?
The oleander plant, like any plant, is susceptible to diseases and pests.
One such disease is called the False Oleander Scale. Scale is a tiny hard-shelled, sucking insect that attaches itself to a plant leaf or stem and sucks out the plant’s sap and nutrients. When there is a huge population of these insects, they look like white spots or blotches on the leaves (source).
Female scale lay their eggs on the underside of the leaves. Nymphs hatch out of the eggs and attach themselves to leaves before drawing out and feeding on the sap. Nymphs mature and lay eggs within five weeks of hatching. A heavy infestation of scale can cause the plant to lose its leaves.
The scale insect can contribute to other pest problems on these plants. It secretes a sugary liquid called honeydew, which coats the leaves and branches. Mold grows in the honeydew and can interfere with the plant’s photosynthesis, causing premature leaf drop.
How To Treat White Spots On An Oleander Plant
The best treatment for scale on the oleander plant is to spray the entire plant with horticultural oil (source). The best time to spray is in the early spring when the new plant growth appears.
Buy a horticultural oil (link to Amazon) and use it as follows:
- Mix two – five tablespoons (1.25 – 3.1 ounces) of horticultural oil with 1 gallon (4.5 liters) of water.
- Pour the solution into a spray bottle.
- Spray the top and underside of all leaves and stems on the plant down to the soil lie.
- Repeat the process in five to six weeks and once more in another five to six weeks.
- Always take precautions when mixing any garden sprays. Wear protective clothing, eyewear, and gloves.
- If the infestation is too big, you may have to prune the plant by snipping off the affected leaves and stems or by destroying the plant completely.
What Other Pests And Disease Can Affect My Oleander Plant?
There are many pests and diseases that can attack your plant and possibly destroy them. Some of these will be visible on your plants, and you will be able to remove the offending insect or cut off the infected leaf, while others are not visible but still cause havoc!
Diseases Which Attack Oleander Plants
Fungi can attack oleander plants, especially plants that are stressed or weakened due to the elements. The treatment for any diseases on your plant would include the removal and destroying of the infected plant and spraying the plant with horticultural oils.
Leaf spot. This particular fungus can cause cosmetic damage to the plant but is not usually a serious disease. Symptoms include brownish patches or dots on the leaves or leaf drop.
Botryosphaeria. Presents as blackened branches during a drought or after a prolonged freeze. This disease can kill the plant.
Sooty mold. Grows in the honeydew excreted by aphids which causes leaf drop.
Bacterial canker. It also creates white spots on leaves, although these spots are raised on the surface of the leaf.
Powdery mildew. Creates white, fuzzy spots, which will cause leaves to turn yellow and wither.
Leaf scorch. Caused by sharpshooter insects, this disease causes drooping stems and yellowing leaves. The infected leaves will turn brown, and the plant will eventually die.
Insects That Attack Oleander Plants
Oleander plants can be attacked by various insects which like to feed on the leaves and shoots. Insecticide sprays can be used to eradicate these pests, but only use them as a last resort as the chemicals in the sprays are toxic and, while effective for use on pests, can also kill beneficial insects in your garden.
Horticultural sprays or the removal of leaves and stems are better methods for eradicating harmful insects without damaging the beneficial insects on your oleander plants.
Aphids. Commonly found on the yellow oleander, this pest pierces the plant and sucks out the sweet juices. An aphid infestation can cause yellow or curled leaves. The plant could have stunted growth or a deformity after a heavy infestation.
Mealybugs. Seen in large numbers on the stems or leaf joints of the plant, these tiny insects harm the plant by sucking out fluids.
Caterpillars. This is the most damaging of all the insects which attack the oleander plant. These pests chew small holes between the leaf vines, stripping the plant of its leaves and small stems.
A mature plant can survive a caterpillar attack, but it will be severely weakened, leaving it susceptible to attack from other pests. Removing the caterpillar is fairly easy as you can see them and remove them from the plant by hand.
How To Prevent White Spots And Diseases On An Oleander Plant
Prevention is always better than cure, and there are ways that you can prevent your plant from being attacked by pests and diseases.
All oleander plants can be sprayed with horticultural oils at the beginning of spring. This should provide them with a protective layer from all insects and diseases as the growing season begins.
Remember to add a layer of fresh soil to your plants and plant food for optimal growth.
- To prevent scale insects from attacking your plants, prune the affected leaves and stems and destroy them so that they cannot re-infect the plant. Sometimes scale insects are easy to see, and if there are not too many of them, they can be removed by hand.
- Do not use insecticides on scale insects as they have a wax coating that will repel the insecticide.
- To prevent fungal diseases like mildew, prune the leaves which have been affected and destroy. Fungal diseases can spread quickly, so catch them quickly, or they will take over the plant. Fungicide can be used on fungal diseases to stop the spread.
- Prevent fungal disease, mold, and powdery mildew by keeping oleander plants dry and well ventilated. A healthy airflow prevents moisture which encourages fungal growth on plants.
- Leaf spot remains in the soil throughout winter and can be prevented from attacking your plants with a good rotation schedule.
- Botryosphaeria and canker. These diseases generally attack a plant that is already in a weakened state from other conditions. Snip off the infected branches and dispose of them away from your garden.
- Leaf scorch. There is no cure for this disease. The best defense against leaf scorch is to spray the plant with an insecticide containing the chemical imidacloprid. Make sure that the product is marked as safe for flowering plants.
- Imidacloprid is highly toxic so wear protective clothing at all times when handling this chemical. Also toxic to bees and aquatic vertebrates, so do not use near rivers or dams.
To keep your oleander plants safe from insects and diseases requires some intervention from your side. With a small bit of planning, your plants can be healthy and disease-free.
These plants are a wonderful addition to any garden as not only are they beautiful to look at, but they also attract beneficial insects to your gardens, like ladybugs and bees.
Keeping them healthy and disease-free will produce lovely plants and will add to the beauty of your garden.