Most common palm diseases | First Aid guide for palm trees

oktober 19th, 2017 · No Comments

rescue-team
In Northern Europe, palm trees do not grow naturally. When cultivating palms is such conditions, a number of things must therefore be taken into account. But even with those precautions, something can still go wrong. This manual explains the main issues and remedies.

Brown or dried leaf tips

One of the most common symptoms but which can have many causes. First of all, it is necessary to check whether all the natural needs of your palm species are met: water, light, humidity and temperature. For a detailed explanation of the general care of palms, please take a look at this page: palm trees care.

If the problem is not the wrong care, it may be due to one of the following causes:
wallpaper 16 1024x768Pest? See further below
Frost damage? See further below
Growth? When only the lower leaves dry out, but the other, newer leaves and spear still look good, you don’t have to worry, this is part of the natural growth process. Once the lower leaves have completely dried out, remove them.


Brown ‘rusty’ stains on the leaves

verbrandingRusty colored stains are visible on the leaves, often the finer leaflets. This indicates sunburn. Check the location of your palm and move the palm if necessary. Palm seedlings and palms that have been indoors for a longer period of time (including those from garden centres!) must slowly get used to the sun. In other words, the number of hours of direct sunshine must be gradually increased. The places that have already been burned do not recover.

bruine-vlekkenBlack / brown dots on the leaves

These stains indicate root damage. The soil is often too wet. Check the correct needs of your palm and adjust the conditions accordingly. This condition often occurs after the winter months when it was logically far more humid for several months. Always ensure proper drainage to prevent root rot.

Leaves turn yellow

geel-bladThis discoloration may indicate a lack of nutrition and in particular a lack of iron. The application of special palm fertilizer gives the plant all the necessary nutrients. In extreme cases iron chelate can also be used which specifically addresses iron deficiency. Use liquid fertilizer for quicker action or a pellets for a more natural and longer lasting effect.

Winter / frost damage

Palms that have suffered from too cold temperatures (frost) show dark green striping in the leaves. These are the first signs of leaf damage. When the leaf freezes too far, these strips turn into brown/yellow spots afterwards. In extreme conditions, even the whole leaf crown can dry out.winterschade1To check if the palm is still alive, gently pull the spear. If it is still tightly attached, the palm will survive, even though it will take some time before the palm has a new beautiful crown of leaves. If you can pull the spear (spear rot) the palm is basically dead.

You can however still try 2 things. First you can fill the gaping hole in the heart of the palm with a Bordeaux mixture to prevent further rotting. Cover to hole from rain.
winterschadeThis will counteract the spear rot. You can also cut the trunk down to the solid part, slice by slice so that the rotten part is removed.

Also see How to treat spear rot

Leaves dry out

When the leaves dry out, and this could not be due to:

  • winter damage
  • sunburn
  • pest
the cause must be sought at the roots! It is therefore advisable to check the roots of the palm thoroughly. There are several possible causes:

The roots must be nice and fresh colored and should certainly not feel soft or smell mushy. If the roots are not in good condition, the rotten parts must be cut away. Then plant the palm in drier potting soil and limit water gifts until the growth resumes.
Sometimes young palms are dug out to only be potted a few days later on for selling. The palm has been temporarily unable to absorb sufficient moisture while the leaves have been continued evaporating water. These palms will show quickly their difficulties. It is advisable to confront the seller with this problem as the natural recovery takes a long time (sometimes up to 2 years without evolution!)

If the roots are black, a fungal infection is at the cause. Fusarium is mainly found in Northern Africa, where it is called “Bayoud” and affects entire date plantations. This fungus that loves warm humid conditions lives underground, from 0 to 100 cm deep and climbs through the roots to the palm leaves where it causes the leaves to die off slowly by preventing water absorption. There is no treatment against this infection and the palm dies completely between 6 months and two years. The affected specimen is best insulated and destroyed, the garden equipment must be thoroughly disinfected. Replanting in that place is strongly discouraged as the fungus can survive underground for up to 8 years.

Also see: Phoenix roebelenii: why the leaves are dry?


PESTS

Aphid or Plant lice

bladluis1The aphid is not always immediately noticeable, but is easy to recognize during more thorough inspection. These insects of half a millimeter are usually green, but sometimes also black or red. They are located on the youngest parts of the plant and propagate quickly, so you will soon have to deal with a real plague. Small numbers can be manually removed. However, this will no longer suffice in the case of larger numbers. The natural enemy of the aphid is the ladybug. But using them as control agents is only effective in a small and closed area like a greenhouse. The plants can also be treated with a solution of water and green soap. You can also make a solution of water with a some of tobacco. After a night soaking, pour the product into the potting soil. The plant will incorporate this solution in the sap flow and thus remove the aphids itself. Eventually you can also opt for a standard pesticide. There is a large range of both chemical and biological products against aphids.

honingdauwScale insect

These small brown to black insects with a flat scale shield hardly stands out because they are immobile on the plant. They stick to protect their vulnerable base. The sticky separation (honeydew) that occurs on the leaves is more striking. The palm is suffering a lot from the suction damage. Scale insects are note caused by a wrong care but occur mainly by coincidence. Small numbers can be removed manually.

schildluisIf necessary, they can be tipped with a cotton swab soaked in spirit. Or the plant can be sprayed with a solution of soap and spirit (mix 2 tablespoons spiritus, 2 tablespoons of green soap and put them in the sprayer), thanks to their shield they are relatively resistant to regular products. So choose a product that is specially designed to treat scale insects which often containing effective oils. Pesticides that are absorbed by the sap flow are also effective. Preventive measures can be taken to mix some tobacco in the top layer of the potting soil. This will be included in the sap flow when watering and will thus repel the insects. Pills are also sold that are placed in the potting soil for prevention. This preventive approach also works through inclusion in the sap flow but isn’t effective enough for treatment once already infected.

Mealybug

Mealybug can be recognized immediately as small groups of white fluff, almost similar to mold. This is one of the most stubborn pests for the plant that can hardly be removed. When you see these insects at the time of purchase, you better avoid the plant. Infected plants are also best removed from other healthy plants. Treatment is absolutely necessary where only a strong product will have the intended effect. Repeated treatment is certainly necessary to eradicate future generations. Thoroughly treat all parts of the plant. Each garden centre offers suitable products.

Spider mite

spintThese very small red or white spiders, the size of a pin button, are difficult to see with the naked eye. But the palm itself clearly shows that there is something wrong. Usually it starts with silver-colored speckles on the leaves. Eventually the leaves become dry and withered. Wooly spider webs can be found on the petioles. In general, spider mite indicates that the location has a humidity that is too dry. This is why they generally occur in palms kept indoors. During the winter months, the central heating system ensures low humidity. To compensate for this, you can regularly spray the leaves with a plant sprayer. A summer rain shower will also be a virtue for the palm.  Spider mite forms a persistent pest. Spraying alone will not always be enough. The best way to remove contaminated plant parts is to remove them. You can also chemically fight the spider mite.

Palm butterfly (Paysandisia)

palmmot 3This moth, called the Paysandisia archon, was introduced in Europe by the importation of palms from South America. Its originates from Argentina. In Europe, for the time being it is only spotted in southern regions (France, Italy, Spain, Portugal,…) Luckily it is not a great traveler but palms that are close to the infected palm certainly form a potential host. The eggs in the size of a grain of rice are laid in the petioles by the moth that can grow about 11cm in size.

palmmot2Because the hairy trunk makes it easier for eggs to be deposited, Trachycarus and Chamaeropses are the main victims of this insect. The larvae can reach a length of 8cm. They eat their way through the palm, making holes in the trunk visible. The leaf also shows a typical damage of the gnawing. At the base of the palm and on the trunk there is also a kind of sawdust, the material formed and rejected by the gnawing larva. When the contamination is too advanced, the palm will have to be destroyed by the complete combustion of the palm. palmmot1

Red palm weevil

grubsrpwcoconut1 copy
Originally from India, the Rhynchophorus ferrugineus caused a great deal of damage in the Middle East in the early 20th century. Meanwhile, there have also been cases in Spain and southern France. All stages of this pest, egg, larva and pupa are spent inside the palm. The female lays up to 300 eggs in a wound or cavity of the palm. After 2 days the larva comes out of the egg that eats its way right through palm for 1 to 3 months. Chemical control comes often too late in many cases. In that case, the only solution to prevent further contamination is to remove and burn the palm.

rpw_adult5

Please refer to this article for a complete description: The palm moth & Red Palm Weevil: everything you need to know!

Caterpillar

rupsIn general, palms are not so often affected by gnawing. The stiff leaf will be partly responsible for this. Young seedlings sometimes become a caterpillar victim however. The traces of gnawing are easy to recognize due to large irregular pieces of the leaves being cut. Sometimes the caterpillar is already nestled in the cocoon. The leaf segments are then glued together with its webbing. When you see traces of gnawing, check the whole plant for the presence of caterpillars. Simply remove the caterpillars by hand. Also the caterpillars that are already nestled in the cocoon. This problem is hardly ever widespread and therefore there is no need for further control.

Cat

Bladschade kattenvraatThe fact that cats and palm seedlings are not a good combination has been proven many times. Cats like to chew on grassy plants for the hairballs to run out. This damage is recognizable by the winky remains that remain after chewing. If the cat has also broken the spear or the small stem, the seedling can no longer be saved. Only preventive measures can help to tackle this, such as removing or protecting the seedling.  Putting the pot in a big glass jar can be a simple and aesthetic solution.

OTHER INSECTS

Springtails

We regularly receive the question what can be done against the small white insects in the potting soil. However, these springtails are not harmful to the plant at all. On the opposite, they live on fungi and thus prevent the formation of mold on the potting soil. They are therefore very much appreciated in the seed trays kept on high temperatures and high humidity will otherwise quickly mold.

Dark-winged fungus gnats

varenrouwmugThis little fly, closely resembling the fruit fly but slightly smaller lays its eggs in moist soil. The flies are not so much harmful as annoying. They propagate very quickly, which make you find these flies about everywhere in the house quite quickly. However, the larvae can be harmful to weaker plants. To combat the flies, yellow catch strips can be placed in the potting soil. The flies are attracted by this and then will stick to the strip. The vacuum cleaner can also be used to suck up all flies. When knocking against the pot, most flies usually will fly up from the ground. Make use of this to catch as much as possible. If this is repeated daily during one week, the problem will largely be resolved. The potting soil can also be poured with a extract of tobacco. This is harmless to the plant but kills the larvae. Eventually you can also use an effective chemical control.

Of course, this is not an exhaustive list of all possible diseases and pests. The phenomena discussed are the most common. If there is a disease or plague that you would like to add in the list, please let us know!

© La Palmeraie


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