The Adenium genus, better known as desert roses, are wonderful sights. Some, such as Adenium arabica, feature swaths of wonderful blooms as bonsai plants and are treasured among bonsai enthusiasts.
Others are popular additions to succulent collectors or in desert-themed gardens with their thick succulent trunks (caudex). Requiring relatively little care, the desert rose is a collection of plants sure to please.
Unfortunately, these wonderful shrubs aren’t immune to common problems like diseases or infestations, and many other common ailments will affect them.
While less common indoors:
- Aphids on succulents
- Succulent Mealybugs
- Plant Scale
- Spider mites
- Mealy bug
… can be a big problem outdoors.
Additionally, oleander caterpillars may attack, as Adeniums (especially Adenium Obesum) are often grafted onto oleander stalks.
Meanwhile, Anthracnose can be a big issue, and root rot (look for black spots) is a major threat to overwatered plants.
Thankfully, all these problems are treatable and can be remedied before any damage becomes terminal – IF treated early on.
How To Control Desert Rose Pests And Diseases
Treating your Adenium plants or Desert Rose for pests and diseases is thankfully not too difficult, although it may need some TLC afterward to regain its former glory.
Prevention is a great way to reduce the risks of the most common problems and should always be considered.
Common Pests
As mentioned, four major garden insect pests will attack desert rose plants.
Aphids, mealybugs, and scale are all related, while spider mites are a type of tiny arachnid.
All four species love to hide on the undersides of leaves and will drink the sap, causing leaves to turn yellow and eventually die.
Additionally, some of the sap will pass through their bodies, creating sticky feces known as honeydew.
Other insects that favor desert rose plants include leafcutter bees, hoplia beetles, thrips, and some other bugs.
Honeydew attracts ants (who will protect aphids and mealybugs from natural predators) and may cause sooty mold, a topical fungal infection.
The good news is all four pests may be treated using the same methods.
Parasitic wasps are a popular outdoor solution, as are ladybugs.
Both of these natural predators may be purchased and are quite effective as long as they remain in your garden.
As you are most likely growing your desert rose indoors for at least part of the year, natural predators may not be an option.
Instead, you may wish to go with neem oil, which is a safe, all-natural remedy.
Using an insecticidal soap is also an effective way to control these pests.
Oleander Caterpillars
As their name suggests, oleander caterpillars love to munch on oleander.
This can pose a problem for many desert rose growers, as it’s a common practice to graft adenium onto oleander stalks.
These grafts result in faster growth and fuller blooms but also attract several species of oleander moth, which lay their eggs on oleander plants.
Oleander caterpillars can rapidly defoliate a plant, although they rarely kill their victims.
The easiest treatment against these caterpillars is to don some gloves and pluck them off.
Follow this up by applying Bt (Bacillus thuringiensis) at dusk on spots where the caterpillars were feeding to kill new larvae when they hatch.
Reapply every 10 days until the problem is gone.
These caterpillars can defoliate your plant very rapidly, but if this happens, don’t despair. Once the caterpillars are under control, the plant will spring back with new dark green leaves very quickly.
The Fungal Adenium Disease Anthracnose
This disease is actually an entire genus of fungi (Colletotrichum) that have similar symptoms and effects.
Anthracnose spores are easily transported by wind, water, and soil, making this problem difficult to get rid of.
Even worse, Anthracnose can overwinter, meaning you will need to work hard to eliminate this fungal disease once it arrives.
Remember that this overwatering can worsen this disease.
If your plant’s leaves develop tan lesions, turn yellow, and fall off, Anthracnose is probably the problem. Symptoms of an infection can resemble frost damage before the plant buds.
Leaves will display round or irregular lesions of a darker or browned tone, dead brown leaf margins, and dead areas along the veins.
The undersides of infected leaves or plant tissue will have tiny bumps visible under a magnifying glass.
While not life-threatening to the plant on its own, Anthracnose infections can significantly weaken your plant, leaving it vulnerable to infestation or other infections.
To treat an Anthracnose infection, prune away any affected branches and leaves, sterilize your tools after each cut, and make sure the clippings don’t come in contact with healthy parts of the plant.
Dispose of any infected clippings, preferably through burning.
Spraying the foliage with fungicide will also help.
You may also need to replace the soil, disposing of the old soil so it cannot infect any further plants.
While there are fungicides available to treat severe infections, neem oil is a much safer alternative and will also work as a preventative.
Again, don’t despair. This disease usually occurs in the early summer and/or in the autumn and resolves on its own. Reduce watering and collect fallen leaves to remove the fungus spores. Your plant should recover nicely.
Watch out for excessive moisture from too much water that can cause stem rot in the impala lily. Do not use a growing medium with poor drainage. Plants do best when planted in a pot with drainage holes and growing in full sun.
Related: Unleash flower potential with our Guide to Adenium Fertilizer and enrich your Desert rose blooms.
Using Neem Oil to Treat and Prevent
Neem oil is a natural plant extract that may be applied topically but works especially well as a soil soak.
A neem soil soak will fight a wide range of pests without harming earthworms, bees, or other beneficial critters.
Additionally, it has been known to aid in defeating root rot in its earlier stages.
You should only use 100% percent cold-pressed neem oil for soil soaks.
These drenches will last for up to 22 days and may be applied every three weeks as both a treatment and preventative.
When used as a foliar spray, neem oil can still kill pests but will also kill Anthracnose and sooty mold.
You will need to use clarified hydrophobic neem oil, preferably 1% percent Azardichitin content, for topical solutions to avoid chemical burns.
Foliar sprays must be applied at dusk or dawn every other day for 14 days or until the problem is resolved, and may also be applied twice per month as a preventative and leaf shine.
A third method is neem cake.
Neem cakes are generally used as fertilizer but also help fight root rot and can kill soil-based Anthracnose spores.
When using neem cake, be sure to follow all instructions on the packaging and adjust your regular fertilizer as needed to keep a proper NPK ratio for your desert rose.