An unfriendly, squeaking beetle

The list of animals and plants living in a particular area constantly changes with time with new species appearing and others disappearing. Some species arrive on their own natural while others are imported by man and wittingly or unwittingly released in new areas.

During the past decade or so we have been hearing about several insect species that appeared in the Maltese islands. The Asian tiger mosquito is a nuisance and carrier of dangerous diseases. The red palm weevil which also appeared in the Maltese islands a few years ago has decimating many palm trees.

Another alien species that is causing great damage is the mulberry long-horned beetle. This species originated in central Africa. It was first noticed in Malta in 2000. When it first arrived it laid its eggs in black mulberry trees (siġra tat-tut) and later on white mulberry trees (siġra taċ-ċawsli) and has destroyed many old trees.

It has also been recorded on fig trees which are related to the mulberries.

In Malta the mulberry long-horned beetle does not seem to have any natural enemies and is free to reproduce unhindered. The larvae live in deep tunnels which they dig in the branches and are not easily reached by insecticides. The adults are mainly nocturnal and to be effective spraying has to be applied during the night. The adult beetle is large and can reach a size of more than four centimetres. 

The antennae areas long as the rest of the body. When picked up it makes a squeaking noise which probably distracts predators.

The mulberry long-horned beetle has been given the Maltese name ħanfusa tal-qrun twil tat-tut. It probably arrived in Malta as a larva or pupa with wood or logs imported for the wood industry. 

It has not yet spread into the rest of Europe except for parts of France and we should do our best not to let it leave the Maltese islands to spread havoc in neighbouring countries. 

This article was published in The Times 31.10.2012

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