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