Comparing to many other plants, a healthy well-grown palm tree usually doesn’t have many disease or pest problems. That is why it’s so important to avoid any damage to the palm especially during transporting it. Cold or freeze damage is another frequent cause of damage to the palms which attracts unwanted insects and diseases.
This post will help you identify and treat the most common palm tree insect pests and diseases.
1. Palm Aphid
Native to Southeast of Asia, palm aphid appears mainly on the newest growth and occasionally on young fruits. This sucking insect can infest a palm in large numbers.
Resembling a whitefly or scale insect, palm aphid are about 1-2 mm long with oval dark brown body and a ring of white wax around them. While appearing motionless, they can feed on the plant for a long time.
Like mealybugs, palm aphid produce honeydew, which sooty mold fungus feeds on. The honeydew attracts ants which protect the aphids and use honeydew for their own consumption. Palm aphid can attack different palm species but is usually found on Chinese Fan Palm, Coconut Palm, Date Palm, Washington Palm and Alexander Palm.
Treat palm with insecticidal soap or horticultural oil. Keep in mind it will only kill pests on contact, so you have to re-apply it if necessary. I usually use insect killing soap by Safer Brand.
This is an organic product, containing potassium salts of fatty acids, works against wide range of insects including aphids, earwigs, grasshoppers, harlequin bugs, leafhoppers, mealy bugs, mites, plant bugs, psyllids, sawfly larvae, soft scales, spider mites, and whiteflies.
Leady beetles is a natural way to control palm aphid. Avoid spraying them with soap.
2. Palm Leaf Skeletonizer
Palm leaf skeletonizer is a small caterpillar that feeds in large numbers on both surface of palm leaves. It eats away the palm leaf between the veins or the ribs producing dark tube structure that looks like leaf skeleton.
It’s best to spot them early and get rid of them before they cause significant damage. Hose off the larva with high pressure until it’s all gone.
If the infestation is more severe, remove the infected fronds and wash off the rest. It could be somewhat effective spraying it with insecticide containing carbaryl or the biological insecticide.
Mealybugs belong to Pseudococcidae, a family of unarmored scale insects, found in moist, warm climates. Mealybug females feed on plant sap, normally in the palm bud but sometimes also in the roots. The males, are short-lived as they are there only to fertilize the females.
They attach themselves to the plant producing a powdery wax that is used for protection, hence the name mealybug. One mealybug will not hurt your plant, but they multiply quickly creating large colonies.
If a plant is badly affected, the mealybugs may kill it by sucking all the juices out of it. Mealybugs also produce honeydew a sticky material that sooty mold fungus feeds on. The honeydew attracts ants that don’t harm the palm but protect the mealybugs and use their honeydew.
One of the things you can do is to rub your plant with a mix of soapy water and alcohol. Make a solution of 1 part alcohol to 1 part water with some dish soap mixed in, wash down the entire palm. This should slow them down. To get rid of mealybugs completely I like spraying it with insecticidal soap.
4. Palmetto Weevil
Native to Florida, Palmetto Weevil is a large beetle that is mostly attracted to severely wounded and dying palms. It could also attack stressed newly transplanted palms like Cabbage Palm and Canary island Date Palm.
New studies from University of Florida, revealed that it could attack completely healthy palms like Canary Island Date, Bismarck, and Latan palms.
Palmetto Weevil vary in color from black to completely red. Their size also varies from 1.9 to 3.0 cm. The adult weevil lays eggs in the leaf bases that hatch into large creamy to yellowish larvae. It takes about three days for the eggs to hatch and begin to feed on the plant. As the larvae grow, they tunnels into the palm heart, where they feed and then create cocoons from which an adult weevil emerges.
In time, this pest destroys the heart, killing the palm. You may not notice symptoms until the leaf crown topples over.
Minimizing transplant stress in newly planted palms will reduce the chance of attack by palmetto weevil. It could be very difficult to detect a weevil infestation before the severe damaged is done to the bud of the palm.
If you notice them early, treat the palm with insecticidal soup. Usually the only thing you can do is to get rid of the infected palm before the adult weevil emerge.
5. Saddleback Caterpillar
Feeding on the underside of the palm leaves, Saddleback Caterpillar chews large holes in the foliage. The Saddleback Caterpillar is dark brown with a distinct bright green patterns on the back resemble a saddle, thus it’s name saddleback caterpillar.
It has poisonous spines that can cause burning sensation like a bee sting if touched with bare hands. It could be found on following palms: Alexander, Chritmas, Fishtail, Cococnut, Princess, Butterfly, Mazari, Canary Island, Pygmy Date, Queen, Mexican Fan palms.
Use biological insecticide to control young caterpillars. Remember to wear gloves to protect your skin.
6. Scale Insects
If you found a lot of little circular, brown colored scales on your palm tree you are in trouble. It’s called “palm leaf scales”. Florida red scale, thread scale, Magnolia white scale, and soft brown scale are among common insects known to attach palms.
You would never guess, but palm leaf scales are actually a mature female small insect. They literally are just a small headless, legless bump and once the female has matured, it is unable to move from where it has planted itself. These small brown bumps tend to focus on new fronds.
Palm leaf scales damage the palm tree by inserting a straw like appendage into the palm tree and sucking the fluids out. One scale will not hurt a palm tree, but as they multiply, the sheer numbers can slowly kill the palm tree. They are both common and damaging to palms and are very difficult to kill.
Palm leaf scales are very difficult to get rid of but it can be done. Typical treatment for palm scale is to repeatedly spray the palm tree leaves with horticultural oil or a mixture of equal parts rubbing alcohol and water mixed with some dish soap.
If you have the patience, you can paint straight rubbing alcohol onto each scale individually. Here is what you need to do:
- Get yourself a small spray bottle, some rubbing alcohol and some dish soap.
- Mix up equal parts rubbing alcohol and soapy water.
- Now what? Yeah. Go spray your palm tree thoroughly.
This will slow the scale down and you will definitely see a difference in the number of scales on your palm tree, but keep in mind they are really hard to kill. To get rid of them completely use a good quality insecticidal soap.
Just spray entire palm with this solution once a week for few weeks. The first treatment will kill immature scale and adults, but eggs under the shell might survive. The second treatment should get rid of the newly hatched crawlers and young scale.
7. Spider Mites
These pets are not true insects but are rather members of the spider family. They develop on the plants grown indoors or in dry conditions. There are many species of spider mites that feed on palms, but the most common one is the two-spotted mite.
You will notice yellow spotting or stippling in the leaf. In severe cases the leaf becomes pale or appears washed out with the webbing on the underside. The mites are small white tiny moving dots that are hard to see without a lens.
To get rid of spider mites treat the palm with horticultural oil, insecticidal soap, or miticides.
8. Coconut Mite
As you have probably guessed from the name of this pest, it only attacks the coconut palm. This tiny mite feeds on the husk of the coconut fruits casing mostly cosmetic damage. In case of extremely large and dense population, the distortion of the fruit and premature fruit drop might occur.
Since mite is so tiny, its very hard to detect. But even after detection, coconut mite is very hard to get rid of by using chemicals. Most palm owners just prune all of the coconuts in all stages of development.
9. Royal Palm Bug
This native to Florida and Cuba bug only attacks Royal palms. This tiny yellow green bug feeds on the young palm leaves of the palm. The female bugs deposit their eggs between the fold of the newly emerging leaflets.
After 8-9 days the eggs hatch. When leaf unfolds it appears scorched and brown and usually fails to mature. These bugs rarely kill the palm but can cause significant damage.
The best way to fight this pest is by applying a insecticide spray. If the palm is too tall to spray without special equipment, drench the soil at the first sign of an infestation.
10. Leaf Spots
Leaf infections called “leafspots” are caused by a variety of fungi and some bacteria on many trees. Leaf spots can be circular to elongated, brown and possibly oily in appearance.
The spots will vary in size and color depending on the plant, the organism involved and the stage of development. It is difficult to differentiate among the leaf-spotting fungi by visual symptoms alone.
Leaf Spots is usually a secondary problem developing on the nutrient deficient palms or the ones with a damage.
Don’t allow irrigation to wet palm foliage. In most cases, leaf spots will not kill the palm tree, and fungicides are usually not necessary. If damage is becoming severe, fungicidal sprays containing copper hydroxide or copper salts of fatty acids can be used. If only a few fronds have been affected, it’s easier just to remove them.
11. False Smut
False smut or Graphiola leaf spot is caused by Graphiola species. This disease is most common in areas of high humidity. Small, black, wart-like bodies are seen, often with yellow filaments protruding from the middle of the raised spots.
Both sides of the leaf are affected. A high incidence of the fungus on leaves can lead to premature death of older leaves. There are usually no symptoms on the youngest leaves. This is a common disease of date palms in south Texas, but chemical control is seldom required.
Properly space palms so that there is plenty of air circulation to reduce humidity. Avoid wetting fronds during irrigation. Removal and destruction of severely infected palm fronds will help minimize disease spread.
However, removal of too many fronds may be more damaging to the palm tree than the disease. Palm trees are sensitive to nutritional deficiencies and frond removal can worsen existing problems and weaken the tree.
Fungicides are usually not necessary but can be applied as a preventative treatment during the spring. Select a fungicide containing copper hydroxide or copper salts of fatty acids. If palm trees are used for food purposes, copper fungicides are the only approved fungicides.
12. Sooty Mold
This superficial fungal disease often feeds on honeydew produced by mealybug, palm aphid, and scale insects infestation, forming a black covering on the leaves. It’s always associated with an infestation of the insects.
Sooty mold appears on the leaf surface and sometimes the trunk. It does not attack plant directly and easily washes off. To prevent the problem from reoccurring, control the sucking insects that produce honeydew.
13. Bud Rot
This common disease usually encountered in palms during hot wet summers. While bud rot tends to occur after a tropical storm or periods of excessive rain, bacterial bud rot tends to occur after the bud has been damaged by cold weather.
Regardless of the pathogen, disease symptoms are similar. The new frond becomes discolored and wilts, followed by discoloration of the next newest leaves. You can also notice black lesions on the new palm spears. Then the bud starts to rot.
Over time, this area may become slimy and get secondary invaders. Older palm tree fronds may remain green for several months and are the last to die. Eventually, only the trunk remains.
In early stages, drenching bud with fungicide that contains fosetyl-Al, propamocarb or mefenoxam ca be effective. Avoid overhead irrigation when possible.
It might be too late for the palm if the new spear pulls out easily and the next newest one is already brown. Infected palms should be removed and destroyed promptly to reduce disease spread.
14. Ganoderma Butt Rot
This disease is caused by the fungus, Ganoderma zonatu , which can infect many types of palm trees. It usually attacks older palm trees that are 15 or more years old. The first symptom of infection is the withering and drooping of older fronds.
Fronds collapse and droop parallel to the trunk. New growth is stunted and is pale green or yellow in color. The head of the infected palm tree may fall off or the trunk collapse. Depending on the point of invasion, palm tree roots may be severely decayed.
Outer trunk tissues may seem solid, but affected palms have a hollow sound when tapped. Areas of dark brown tissue are evident when the trunk is dissected. Over time, conks (spore producing structures of this fungus) may form.
It looks like a white spongy growth at the lower portion of the trunk (the butt of the tree, thus the name Butt Rot) that turns brown as it matures. Palm tree death can take three to four years, depending on the age of the tree and environmental conditions.
This fungus survives on plant tissue, so remove and destroy any root systems, stumps and trunks of dead palms in the landscape. Removing the conk will prevent spores from spreading to other trees.
Ganoderma survives in the soil, so it is not recommended that another palm tree be planted in the same location. Unfortunately, there is no chemical control for this disease.
Avoid any injury to the palm tree, especially during planting, staking and regular maintenance activities by string trimmers and lawn mowers.
15. Lethal Yellowing
Lethal Yellowing is a deadly disease caused by a mycoplasma-like organism which is a bacterium whiteout cell walls. It is commonly spread by a sucking insect Myndus crudus.
After feeding on the infected palm, the leaf hopper bug moves to a healthy one transmitting the disease. The first signs of the disease is the blackening of young flower and fruit stems following by a premature fruit drop. On most palms, the older leaves will turn yellow, grey or brown first until the whole canopy wilt and die.
Unfortunately, there is no cure for lethal yellowing. Periodic injections of antibiotic can help prevent it from progressing. If treatment is stopped, the palm tree will die.
16. Fusarium Wilt
This native to California fungal disease can now also be found in Florida. On infected palms the leaflets on only one side of the leaf stem of the oldest leaves start to turn brown and then die. The fronds develop a reddish or dark brown strip along the leaf stem.
Eventually, all old leaves turn completely brown. Then it moves to the new emerging fronds. It can take from a few months to two years for the palm to get overpowered by the Fusarium wilt and die. Coconut palms, Mexican palms and Date palms have been the worst affected by that disease.
There is no treatment for this disease, but it can be stopped from spreading to other palms by disinfecting pruning tools between trees.
17. Bacterial Bud Rot
It causes a wet blight of the emerging spear leaf which can spread downward to the bud. Affected leaf spear often will pull easily from the bud. A foul odor can also be present. This disease usually affects cold damage palms.
Bud drenching with copper-based fungicides can be affective. I recommend applying it before the cold snap happens.
Generally, insects and diseases attack weakened trees. Healthy palms resist insect pests and diseases. So, staying on top of the nutrient levels and winter protection is the key to keeping your palm healthy.
And of course it’s better to catch insects and diseases in early stages before they overpower the tree and become fatal. Look for new growth that have died back or fronds that are discolored, spotted or frizzled. All these signs indicated that something is wrong with your tree.
One of the products I use against different type of fungus is Copper Fungicide spray by Bonide. It’s a great fungicidal spray that helps control many diseases including powdery mildew, downy mildew, black spot, peach leaf curl, rust, and others.
For insecticidal soap I like Safer Brand Insect Killing Soap. This spray always worked for me on all kind of insects including aphids, earwigs, grasshoppers, harlequin bugs, leafhoppers, mealy bugs and mites psyllids, sawfly larvae, soft scales, spider mites, squash bugs, blossom thrips and whiteflies. It’s organic formula will help you get rid of bad insects, but won’t harm beneficial insects.