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.