Weevils On Sago Palms – How To Control Palm Weevils


By: Teo Spengler

The palm weevil is a serious pest of palms. Native to Southeast Asia, it is the pest that causes more damage to palms than any other. The insect pest has spread to most continents, including Africa, Asia, Europe, Oceania, and even North America. Weevils on sago palms cause extensive damage and many gardeners are asking how to control palm weevils. Read on for information about palm weevil damage and sago palm weevil control.

Palm Weevil Damage

Weevils on sago palms can kill the plants. The eggs don’t damage the plants, nor do the weevil adults. It is when the weevils are in the larva stage that palm weevil damage occurs.

The life cycle of the palm weevil begins when the adult female weevils lay eggs on or near the sago palm trees. The larva hatch out of the eggs in a few days, and bore into the living tissues of the tree. The weevils stay in the larval stage for up to five months, digging holes in the trees. The damage from weevils on sago palms can be so severe that the trees die within six months.

When the larva stops eating the living wood of the tree, it builds a cocoon out of palm fibers. The cocoons of weevils on sago palms are usually located inside the trunk of a leaf stalk. The adult emerges from the cocoon after about 20 days and sets to mating and laying more eggs.

Sago Palm Weevil Control

Anyone with a sago palm needs to know how to control palm weevils. Palm weevil treatment involves a combination of control methods including removal of infected wood, applying insecticides and trapping the adults.

When you want to remove weevils on sago palms, the first thing to do is to remove the dead parts of the tree. Then cut out the plant parts infested by larva with a sharp cutting tool. If the entire trunk is affected, you cannot save the tree. Your best bet to prevent the weevils from spreading to other trees is to remove the infested plant, roots and all, and burn it.

If the tree can be saved, the second step in sago palm weevil control is to spray the palm with insecticide. You can inject systematic insecticides directly into palm trunks as well. Applying systematic insecticides to the soil helps to eliminate the weevils in the egg stage. When you use insecticide as a palm weevil treatment, you must repeat the application two or three times every year.

Another effective method, often used along with insecticide, is trapping the adult weevils. To use this sago palm weevil control method, you use aggregation pheromones that attract the females. Place these pheromones in a container together with insecticide to kill the weevils.

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Product Overview

Safari 20SG Systemic Insecticide with Dinotefuran is a super-systemic insecticide with quick uptake and knockdown, and controls a broad spectrum of ferocious and invasive pests, including Q- and B-biotype whitefly, hemlock woolly adelgid, emerald ash borer, mealybug, leafminer, fungus gnat, black vine weevil, glassy-winged sharpshooter, armored and soft scale and lacebugs some of the most costly pests that affect high value greenhouse and nursery crops such as poinsettia and hibiscus, as well as trees, shrubs and herbaceous ornamentals in the lawn and landscape market.


Vine weevils

Vine weevils are a devastating plant pest – suddenly otherwise healthy looking plants wilt and collapse and no amount of watering will help them recover. The reason? The vine weevil grubs have eaten all the roots.

Description

Vine weevil grubs are particularly rampant in containers, but they also attack plants in borders and beds, where dealing with them is far more difficult. The real danger is the underground grub - you can’t see what they’re doing until maybe it’s too late.

Symptoms

Baby vine weevils grow from little eggs laid in the plant’s roots - which are very difficult to see. They hatch into 10mm long ‘C’ shaped grubs with cream coloured bodies and brown heads. The little vandals, unseen, simply munch away at the root system until either they are caught or the plant first yellows, then wilts and collapses through lack of sustenance.

Adult vine weevils are dusty grey/black flightless beetles. They are all female and each can lay up to 1,000 eggs in a season. Eggs are laid during the summer and early autumn ready to become grubs in spring the following year. These beetles do most of their eating at night and restrict themselves to nibbling away at the edges of leaves. The results are unsightly but not life-threatening to the plant. However the energy they get from eating ensures that the eggs will be laid. So they can’t be ignored.

Treatment and control

General tips

Adult vine weevils are pretty resistant to sprays. It is best to physically remove them. Collect them, by torchlight, at night whilst they are feeding. Place a newspaper, a tray or something else that will catch these flightless beetles and ‘knock’ the plant to dislodge them. Pick them up, squash them and bin them.

Drench the compost

It is possible to kill the adult larvae that feed on plant roots by drenching the compost in which ornamental plants are growing with a systemic insecticide.

Treating edible crops

There are no recommended insecticides approved for treating edible crops.

Biological control

Introduce pathogenic nematodes. These are little parasitic worms which will do no harm to the plant but which will kill the vine weevil larvae with a fatal disease. As with most biological controls the conditions need to be absolutely right for the treatment to work.


Yellowing

If you spot new growth that turns yellow, this may be an indication of a nutrient deficiency, namely a lack of sufficient quantities of manganese.

If you notice yellowing, you can supplement with manganese sulfate. Keep in mind that this is not the same thing as magnesium sulfate, the active ingredient in Epsom salts. Fronds that have already begun to turn yellow will not recover, but supplementing with the proper nutrients will help to restore good health to the rest of the plant.

Yellowing on new foliage may also be an indication of poor drainage, or overwatering.

When I had the occasional problem with yellowing or fronds dying off on my patio in southern California, we were in the middle of a drought, with occasional flood rains in the winter just to change things up. The plants predated my arrival at this location as a tenant, already planted in sturdy, incredibly heavy containers on the back patio.

I never amended the soil, and I couldn’t tell you whether they had good drainage in those containers or not. Honestly, I was just happy to have something already living that was growing relatively happily when I moved in.

These sagos were located in partial shade and they were watered occasionally by myself, or by a landscaping crew hired by the landlord that paid little mind to the actual needs of the plants (ask me about the time they lobbed off the top three feet of the cacti that were also growing there, to my horror).

Since they were potted, these plants were not very large. The frond damage eventually resolved itself, with dead foliage that was easily clipped, or that would dry and fall off on its own. This didn’t affect the overall health of the plants, and it was safe to assume that this was not a sign of disease since the problem did not spread.

Fronds will also begin to turn yellow with age, eventually shriveling and turning brown. This isn’t a sign of an unhealthy plant, but rather, simply a process that is typical of cycads. Dead fronds can be removed.

Fertilize regularly to prevent or treat a nutrient deficiency. Follow package directions for the size and location of your sagos, whether grown in the ground or in a container. Soil testing may also help you to determine exactly what it is that your soil lacks.

Furthermore, don’t go crazy with the watering! Established cycads are drought resistant, and should be planted only in well-draining soil that is allowed to dry out between waterings. Standing water or saturated ground is not your friend if growing these plants.


Is there a way to save the palm trees on the French Riviera? Notes on Rhynchophorus and Paysandisia.

F For years there have been reports about the two main pests damaging Mediterranean palm trees, the so-called palm moth (Paysandisia archon) and the so-called red palm weevil (Rhynchophorus ferrugineus). Both insects have been featured by various publications, as „immigrated“, i.e. non-endemic, pests: the palm moth originates from Uruguay and Argentina, while the red palm weevil calls tropical regions of Asia his original home.

Unfortunately it is climate change that not only allows us to plant exotic species on the Mediterranean Sea, but that also helps plant pests to spread that were unknown so far.

It is quite urgently necessary to act both, systematically and persistently, against these palm pests, because not only is it highly expensive to dispose of a palm’s old, dead trunk. In some regions on the French Riviera complete, once magnificent, avenues have already been destroyed: whoever is looking for an exceptionally devastating example will make a sad find in HyГЁres.

A big problem with fighting these two pests consists in the high number of second homes on the CГґte d’Azur, where many gardens lie unobserved during autumn and winter, when the larvae of both insects have an exceptionally easy run on their victims.

For simplicity reasons we will confine ourselves to the Latin names hereafter, in order to help with the exact identification among the different languages spoken on the Riviera.

Which palm trees are attacked by the palm moth (paysandisia)?
Butia yatay,
Chamaerops (all species),
Phoenix (canariensis/dactylifera/reclinata),
Latania,
Livistona (chinensis/decipiens/saribus),
Sabal,
Syagrus (romanzoffiana/yatay),
Trachycarpus fortunei,
Trithrinax campestris,
Washingtonia (all species and cultivars, including filifera, slightly less often though).

Which palm trees are attacked by the red palm weevil?
Areca catechu,
Arenga pinnata,
Borassus flabellifer,
Caryota (maxima/cumingii),
Cocos nucifera,
Corypha (gebanga/elata),
Elaeis guineensis,
Livistona decipiens,
Metroxylon sagu,
Oreodoxa regia,
Phoenix (canariensis/dactylifera/sylvestris),
Sabal umbraculifera,
Trachycarpus fortunei,
Washingtonia (all species and cultivars, including filifera).

The species that are predominately planted on the French Riviera, Chamaerops, Phoenix, Livistona, Trachycarpus and Washingtonia are attacked by at least one of the two pests. Since for a number of reasons we may not hope that these pests neither will nor can be contained on the Mediterranean, at least not on short notice, we must raise the question of which species should be chosen for new plantings. Secondly, secure, effective, cost-efficient and practicable solutions for the prevention and the reduction of the pests’ distribution rates have to be found.

How to recognise an infestation
The pattern of damage on infested palm trees is quite similar with both insects, although an infestation by the palm weevil will lead to the palm’s death even quicker. While in the case of the palm moth, only its larvae will destroy a palm’s leaves, also the palm weevil itself, and not only its larvae, will eat holes and burrows into the leaf stalk’s base.

Both vermins attack the soft (and only) „growth point“ of the palm tree, the so-called apical meristem or vegetational cone, right beneath the crown. As soon as this is destroyed the palm tree, and this is different from most other plants, cannot keep growing, it will certainly die. For this reason a quick and persistent treatment of all palm trees is necessary.

The older and thus higher, the more bushy or overgrown (Chamaerops) and the more armed with thorns (Phoenix) the specific palm tree is, the more labour- and cost-intensive the control of a possible infestation will be. Brownish outlined small holes in outgrown leaves will indicate that at least a while ago an attack must have happened, and that the next generation of vermins is likely to already have left the palm tree. Quite fine, fibrous material that is thickened by dried palm sap and which looks a little like dark sawdust that has been mixed with tree resin, inside of and beneath the crown and between the old cut off bases of leaf stems along the palm tree’s trunk, are a sure indicator for a massive infestation. Horizontally off-standing leaves, that after getting at first yellowish will turn greyish and then will slowly sink down more and more are another sign of an infestation, especially with the phoenix palm tree.

Due to the increasing extent of the problem, it actually seems quite irrelevant, if a palm tree is already infested or not: unfortunately it is only a matter of time, when an attack will happen, particularly because of the fact that at the beginning of an affection of a palm tree, there will be no visible external signs. A systematic prevention of all palm trees is therefore indispensable.

How can infested palm trees be treated and which prevention measures are possible?
In our latitudes, neither the red palm weevil nor the palm moth are affected by any natural enemy. The oviposition of both species usually happens in late summer or early fall. The palm moth is a quite large and ostentatiously gliding about butterfly, a beautiful but treacherous image between September and November. The flying females of the red palm weevil species are admittedly so fast and inconspicuous that they are rarely noticed. Unfortunately the larvae are also frost-proof, which allows them to have an especially easy run on the palm trees during the home-owner’ absence.

Of course there is always the theoretical possibility of fighting pests like these with insecticides with agents like Chlorpyrifos 48%, Dimethoate 40%, Phosmet 50%, Imidacloprid 20% or Thiamethoxam 25%. Other possibly effective insecticides are banned within the EU for very good reasons. All named insecticides are extremely harmful to bees and do have highly negative impacts on other useful creatures, on bird life and the ground water. But even more importantly, since a persistent prevention has to be put in place, the application of these insecticides can’t be stopped, which makes them on a long time scale just too environmentally hazardous, and – given the number of palm trees on public and private land – simply too expensive.

For the treatment and prevention of these pests we would recommend applying nematodes of the Steinernema carpocapsae , which can easily be ordered via Internet. Cooled down (2-6 В°C) they will be storable as a powder for about a week. The whitish transparent nematodes (active phase: 0,1 mm) will look for the vermins, they will percolate into them through their body opening, they will propagate within them and will discharge a bacterium which will kill the weevil or moth within only a few days.

In order to ensure a successful treatment the temperature of soil and air should at least be around 12В°C, otherwise the roundworms are inactive. During winter the nematodes will usually die off. Therefore the nematodes will need to be distributed again during the next season. The treated palm crowns should be kept damp during the following 6-8 weeks after a treatment to maximise a lasting effect. Unfortunately nematodes are sensitive to light and ultra-violet rays. Consequently the treatment should be executed during dusk/dawn or at times with a slight overcast! The ideal temperature in regards to the most effective application would be around 15 – 20 В°C.

The costs will be around 10,- to 30,- EUR (30 to 100 m 2 ), depending on the ordered amount. This on the other hand will be sufficient for quite a high number of palm trees, plus the necessary man hours for the application of the nematodes.

Because of the amount of work needed and due to the severity of the problem, we would now recommend, especially with higher palm trees, which cannot easily be treated from a standing position or from a small ladder, to permanently install a spray nozzle with opening holes of at least ВЅ mm, which are then connected to a small (irrigation)pipe down and along the palm’s trunk. The small nozzle only has to be readjusted every now and then, according to requirement, e.g. after heavy storms or after the palm crown has been maintained by your gardener. From the lower end of the pipe, which stays permanently on the respective palm, one can then easily pump the prepared nematode lotion up into the crown by using a manual water pump. Irrigate the crown amply with the nematode lotion – and ideally monthly. With smaller palm trees, which are easier to reach, you can simply use customary pressure sprayers. Please pay attention to sufficiently wide enough holes in the spray nozzle, so the nematodes can pass them(!), and please also take care to never use the same sprayer, which you already have been using for the application of any poison, like insecticides or herbicides.

Another possibility for fighting the larvae of the two pests lies within the application of the entomopathogenic fungi Metarhizium anisopliae or Beauveria bassiana, which deploy their environmentally friendly effectiveness also with other species of insects. They too can be comfortably ordered over the Internet.

Which other precautions will help to save your palm trees?
Please examine your palm trees on a regular basis in regards to above named patterns of damage and please have a qualified gardener peel, skin and maintain them regularly. A Chamaerops humilis for instance, which is not maintained permanently, will overgrow and get bushy within one season it will develop toward a hotbed for both insect species.

Never leave freshly cut palm leaves lying around for a longer period. If there is no other way than leaving them on your property for a while then please wrap the ends into heavy duty plastic bags or put the cuttings into quite airtight barrels, because the palm sap’s scent is extremely attractive to both species and will be detected even from quite far distances.

Please also instruct your gardener to never enter your property with palm cuttings from other gardens, but to dispose of all palm cuttings beforehand. This may sound a little alarmist but, more often than not, this way these pests are distributed very effectively to properties that had been not-infested before.

Even if more and more arborists and botanists share the (right) opinion that with tree surgeries wound protection lotions should not be applied any more and thus cut surfaces should be left open and unsealed, we would highly recommend to refrain from this otherwise good practise in the case of palm trees and start using wound protection lotions again with palm trees in order to minimise the effect of attraction of the insects through emerging tree sap.


Watch the video: Controlling vine weevil


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