Wednesday, July 21, 2010

The destructive red palm weevil

The red palm weevil has been in the news since it appeared in Malta about three and a half years ago. It is a large rusty-red beetle that lives on palm trees and can kill the host plant. It is a strong flier. 

Last week one flew through my bedroom window in a locality where there are no palm trees within a radius of several hundred metres.

The red palm weevil, which has been given the Maltese name bumunqar aħmar tal-palm, came from tropical Asia from where it spread to Africa and Europe. It reached the Mediterranean in the 1980s and was first recorded in Spain in 1994. In 2006 it was found in France and in 2007 it was recorded from Malta.
The adult weevil damages palm trees through feeding but it is the larva that kills it by burrowing into the trunk.

The cause of the high rate of spread of this pest is human intervention, by transporting infested young or adult date palm trees and offshoots from contaminated to uninfected areas.

Information on Red Palm Weevil was first published in 1891 in India. This pest was first described as a serious pest of the coconut palm in 1906, while in 1917 it was described as a serious pest in the date palm in the Punjab, India.

It is considered as the most serious pest of palm trees in the world. Control is mainly through the use of pesticides although other measures such as attracting the adult insect into traps by means of pheromones are sometimes used. Pheromones are chemicals released by females to attract males.

It has been found that the most effective way to apply pesticides directly into the trees by injecting it directly into the trunk. As happens whenever pesticides are used there can be serious negative consequences to the environment. 

These chemicals leach into the soil and water killing other organisms. In other countries experiments are being carried out to assess the effectiveness of biological methods of control.

One such method is by the use of nematodes that attack the insect killing it within three days but what is effective in the laboratory does not necessarily work in nature.

This is not the only pest that arrived in Malta in the past few years. Another pest which has had serious negative consequences is the tomato leaf miner which last summer destroyed a large percentage of the tomato crop.

This article appeared in The Times 17.03.2010

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