The Adenium genus, better known as desert roses are wonderful sights. Some, such as Adenium arabica feature swaths of wonderful blooms and are treasured among bonsai enthusiasts.
Others are popular additions to succulent collectors or in desert-themed gardens. Requiring relatively little care, the desert rose is a collection of plants that are sure to please.
Unfortunately, these wonderful shrubs aren’t immune to diseases or infestations, and many common ailments will affect them.
While less common indoors:
… 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 of 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 for pests 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 a problem and should always be considered.
As mentioned, there are four major garden pests that 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 yellow and eventually die.
Additionally, some of the sap will pass through their bodies, creating a sticky feces known as honeydew.
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 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.
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 simply 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.
If your plant’s leaves develop tan lesions and then 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, as well as dead brown leaf margins and dead areas along the veins.
The undersides of infected leaves 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, sterilizing your tools after each cut, and making sure the clippings don’t come in contact with healthy parts of the plant.
Dispose of any infected clippings, preferably through burning.
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.
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.