Enjoying a Spanish Evening under the umbrella of a Canary Palm

The other day I received a lovely email from a lady who has 2 mature palms in her garden. They were riddled with palm weevils a year or so agao. I am so pleased to have been able to help keep some of these majestic palms alive! I hope that soon there may be a longer term and more environmentally friendly solution to this problem.

'Sorry I missed you both on your last visit wasn't feeling so good
Well I got sentimental the other night or it could have been a drink or two too many I was sitting outside very late enjoying the night air and the rustle and swaying of the palm trees, and I thought of you both and felt an overwhelming urge to thank you for rescuing them Our patio would never be the same without them, so just a Simple Thank You to you both'
Fondest wishes
Sue Arthur '

Trimming those falling leaves

Pruning palm leaves should be done in December and January when the temperatures are at their lowest and the number of adult weevils flying around looking for new places to lay eggs is at a minimum. The cut surfaces release kairomones attracting the weevils and also provide a nice easy surface for them to drill a hole for egg deposition. If you have leaves falling and causing a nuisance, perhaps in your drive or on the lawn, just trim the end, as far away from the trunk as possible, at least 1.5m -but the further the better. The area of exposed surface will be much less and if an egg is laid the chances are that the hatched larva won't ever reach the inside of the trunk.

Treat palms regularly to protect from Red Palm Weevils

The continual treatment of your palms is laborious and expensive however if you become complacent the result can be disastrous. The nurseries, parks and botanic gardens all treat their palms every 4 weeks without fail, and implement an integrated system using nematodes during the cooler months, mass trapping and chemical crown drenching during the hotter months. These methods of control are to minimize environmental impact by using a biological control which has no effect on any other living organism in the palm other than larval pests, physical trapping and the drenching rather than spraying to minimize drift of insecticide and therefore impacting neighbouring insects, most importantly bees and other pollinators.
The Junta de Andalucia recommend treating within 6 weeks with insecticides. This is because the insecticide only remains active for a 2 - 3 weeks and therefore any eggs laid after this time will happily develop and start eating away inside the palm. It is important to change insecticide so as to prevent any resistance that those young larvae may develop to the one previously used.
Some people have suggested that treating every 3 months or even 6 months is fine.
They have been lucky! Most palms left for such a period without treatment will fall victim to the Red Palm Weevil, especially if there are nearby infested palms.

Hope for Canary Palms

Research is being carried out worldwide to find a solution to the problem of infestation of palms by weevils. At present the use of entomopathogenic nematodes is used widespread in the Mediterranean to control this pest, however, treatments are effective only for a couple of weeks and with such a number of treatments needed annually come at a very high cost. There is hope for the future. A group of biologists in Alicante have been working on the entomopathogenic fungus Beauveria bassiana which infects and spreads causing death of both adults and larvae. The advantage of this treatment is that once applied the weevils transmit the spores to other weevils. Treatments would only be needed 2 or 3 times a year.

Treatment to prevent infestation

Given the characteristics and nature of an infestation by red palm weevils it is vital that it is rapidly detected. To get a reliable diagnosis of the condition of a palm, a specialist company or qualified professional should be consulted. They will be able to advise on treatments or methods of prevention .
There are only some chemical products licensed for preventative and curative treatments, which can be used on their own, combined with or alternating with biological treatments using entomological pathogenic nematodes.
Recommended intervals between treatments are 4 - 6 weeks.
Junta de Andalucia information
Integrated pest management involves a number of strategies to prevent infestation, such as combination treatments and using pheromone traps. Trials in Finca La Concepcion (Malaga) and Finca El Batatal (Marbella) have achieved excellent success in saving infested palms (93%) and there have been very few further cases of infestation.
More information about using traps can be found from Econex (Spanish but click on flag for translation)

What are the signs of an infested palm?

Symptoms include holes in leaves, leaves that appear to be cut in a straight line with scissors, drooping leaf or leaves, dry leaf or leaves, vinegar smell, cocoons in trunk or wedged between leaves, old cocoons on the floor or you may just see lots of weevils flying around - they are attracted by other weevils.

Marbella Palm with Two Crowns

Last week I came across this wonderful palm. Usually a palm only has ONE region of growth (apical meristematic tissue) resulting in just one crown of leaves but this one must have suffered some damage, possibly by the red palm weevil larvae, resulting in a division of the region actively carrying out cell division.

Surviving Red Palm Weevil Attack

A badly infested Phoenix canariensis was treated with systemic and contact insecticides last November. The damage was right in the crown with cocoons emerging from the new growing leaves and a large section was rotten, smelling characteristically of vinegar. Several months on a new leaf, albeit eaten, has emerged on the less damaged side of the palm giving hope of recovery.

List of palms affected by the Red Palm Weevil

Rhynchophorus ferrugineus has had an enormous impact on the landscapes of the Mediterranean Coast. The most obvious victims are the mature Canary Palms (Phoenix caneriensis). Although the preference or indeed detrimental effects are mainly observed on this species, many palms are susceptible and with infestation can also result in death of the palm. The list below details all palms that have been host to the Red Palm Weevil.
· Areca catechu
· Arenga saccharifera
· Arenga pinnata
· Borassus fl abellifer
· Borassus sp.
· Calamus merrillii
· Caryota cumingii
· Caryota maxima
· Cocos nucifera
· Corypha utan (= C. gebanga, C. elata)
· Corypha umbraculifer
· Elaeis guineensis
· Livistona decipiens
· Livistona chinensis
· Livistona saribus (= Livistona cochinchinensis)
· Livistona subglobosa
· Metroxylon sagu
· Oneosperma horrida
· Oneosperma tigillarium
· Phoenix canariensis
· Phoenix dactylifera
· Phoenix sylvestris
· Oreodoxaregia
· Sabal umbraculifera
· Trachycarpus fortunei
· Washingtonia sp.
Also;
· Saccharum officinarum, sugar cane
· Agave americana, century plant
There is some evidence suggesting that the native Chamaerops humilis and the popular Washingtonia filifera demonstrate natural resistance to infestation by the Red Palm Weevil

More red palm weevils in spring and autumn

A few dedicated weevil trappers in Alhaurin el Grande and Cartama have been collecting data for over a year.  Here are the results for our catches in 2010.  It is interesting to note that during the hotter months of July and August  and the colder month of January the number of weevils trapped was lower than the milder months in Spring and Autumn. December was particularly mild which could explain the high numbers caught so late in the year.

These figures are a good indication of the number of weevils in flight and in search of new palms to infest throughout the year and it will be interesting to see this years results for a comparison.  In my own personal trap the figures are already higher than last year(we trapped 90 in January), and as we observe so many  deceased palms, everything suggests that this pest is approaching epidemic proportions!

Red Palm Weevil larvae eat the entire trunk of old Canary Palm!

An article last week shows just how cryptic these insects are!  The palm looked well and healthy but the inside of the trunk was totally hollow. Read about it on this great gardening site: Gardening in Spain.

Trapping Red Palm Weevil (Rhynchophorus ferrugineus) can help reduce and monitor populations

These traps are most effective burried in the ground, soil level with holes in the side.

Spring is here – well almost!  The temperature this morning, just before 9, is already 14^oC and the bees can be heard buzzing happily on some of the flowering shrubs.  They aren’t the only insects that get moving with the warmer weather.  The weevils are out there too.  I am, of course, talking about the Red Palm Weevil – the evil weevil destroying so many palms, young and old. We have caught 11 in my small trap over the past couple of days.  Not such a big catch compared to the 82 we found when the sun shone for a few days in January, but with all the rain and generally lower temperatures, the 11 is a sure sign that THEY ARE OUT THERE – and in their millions.  I have been trapping for over a year now, and this year am catching many more.  This could be because of the dreadful rain we had last year – or simply because there are more weevils about.

If You Don't Care Cut It Down Now !

It is alarming that some people still think that the red palm weevil can be dealt with by pouring washing up liquid over the crown. I suppose that this method was discovered by putting some liquid in a jar and adding a palm weevil Not surprisingly it drowned in the viscose liquid. The same would have occurred using a jar of water. In fact others treated their trees by putting a hose up into the crown and turning on the tap for several hours. Of course they may have been lucky and caught an adult weevil off guard and drowned it but it would not and could not affect the larvae inside the palm, which are the creatures that cause the damage.  Another myth that is still prevalent is that the weevils will not attack baby palms or that once a palm is infected it is to late to do anything about it.

The truth is that there are currently only three methods that could eradicate this plague from gardens and countryside. They are the use of insecticides applied either as trunk injections or crown drench. The ecological method of crown drench with microscopic parasites called nematodes. This is the preferred method in the writers view. Thirdly, the sad fact is that the weevils have no natural predators, therefore the use of traps is the only way to prevent the weevils from laying their eggs in a palm in the first place. These traps are not expensive and use two attractants to the weevil called kairomones and pheromones. These are placed in the container and in conjunction with either a poison tablet or 20mm of water will quickly see the demise of all who enter.

A palm can survive after infestation if spotted and treated in time. Regardless of this an infested palm should be treated whether or not it has any chance of survival. The reason being that each female weevil is capable of laying three hundred eggs and if the three hundred eggs develop into 300 adults of which, lets say 150 will be female. In three generations and each generation occurs every 4 months  more than a million  new weevils will have entered the environment.

One now associates palms with our Mediterranean climate and this has been so for several hundred years. To devoid our environment of the beautiful palms would be a shame on us all. Judging from the experience of the Canary Islands it is possible to get this plague under control but it will take the will of all concerned to achieve this goal. You don’t have to have a palm to have a trap and you could add to the fight against the weevil. If you have one of the palms most at risk, such as a Canary palm, but have no intention of treating it (it is not a question IF it will be infested but WHEN will it be infested) be considerate to your neighbours and have it cut down now!