Miner beetles strike again

NOT WELL: The discoloured nipah palm fronds is a sure sign of coconut leaf miner infestation

April 11, 2010, Sunday


Chai Sue Yee, a coconut farmer in Bako a coastal village near Kuching, is a worried man these days because the miner beetles are back, and with vengeance after a lapse of 10 years.

The proliferation of the beetles spells trouble for him and his fellow farmers.

The adult beetle (reddish brown, 7 – 9 mm long) feeds on the spongy tissue of the leaves by biting a series of grooves on the lower side of leaves. The larva feeds and mines inside the leaves from the lower side as well.

The first sign of trouble for the coconut farmers was the invasion of worms in a nearby village Muara Tebas towards the end of last year.

The creepy crawlies were actually the larvae of the miner beetles and Chai recalled seeing them all over the place even on the dining table when he visited friends in Muara Tebas late last year.
Then there was the telltale sign of palm fronds which looked like they had been licked by fire leaving them appearing burnt and shrivelled.

Chai knew the portends were no good, he had seen these signs before and it could only mean an infestation of the miner beetles.

“The same thing happened in 2000, during that time the Agriculture Department used helicopters to spray insecticide,” he said.

He remembered the chemical used was so potent that it could even kill birds flying around the affected area. So far the invasion of this dreaded insect is confined to the southern part of the state.

Although coconut farmers there are worried, they are not throwing up their arms in despair yet. There is a good reason for them to be optimistic they could weather the infestation because this time round the State Agriculture Department is better prepared to combat the invasion of the miner beetles.

The State Agriculture Department divisional head Michael Ranges said that they had learnt valuable lessons from the last attack 10 years ago and they were not about to press the panic button.

“It is an infestation which normally occurs in the environment which had been infested previously like in Samarahan, Kuching, Bako and Sri Aman,” he said adding there seemed to be a 10-year cycle in the population explosion of the pest.

Michael’s main concern is the excessive use of pesticides by farmers in trying to rid the beetles as the chemicals could cause severe damage to the environment.

The department had learnt a painful reason when it resorted to using helicopters to spray chemicals on the affected areas to kill the beetles in a futile effort to end the infestation 10 years ago.

Michael recalled the cost for the operation ran into millions of ringgit but the effect was minimal as not all the beetles were wiped out and continued to breed after the spraying while damage to the environment was extensive.

If chemical were to be used this time Michael said it would be more localized and done by the farmers themselves.

“Smaller spraying operation can be done by the coconut farmers themselves as they were already provided with the equipment and chemical.”

The last resort would be trunk injection which is potentially dangerous and may cause other effects to the plant and other living organism in the area.

The agriculture officer speculated that there might had been some disturbances in the environment which caused the miner beetle population to explode now.

“It could be caused by climatic condition and its effect to the environment, we are still studying the situation,” he said.

However, Michael believed that nature would heal itself as the beetle had its own natural enemy, a tiny wasp that fed on the beetle’s eggs and larvae, and that with plenty of food the wasp population would increase and bring down the population of the beetles to its natural level.

The good news is this natural way of ending the infestation had happened in the Kota Samarahan area where the situation has returned to normal without the use of harmful pesticides.

The Department’s entomologist Megir Gumbek said: “We have been monitoring the situation in the field and there is a high population of the beneficial wasp, (Pediobius sp.) which parasitises on the larval stages.”

Based on her observation, the infestation was not worrying and the damage wreaked by the beetles so far has not been very severe except for the unusual burnt appearance of the coconut fronds.

However, the impact of natural healing is not immediate. “The good wasp population takes a while to build up; it may take two to three years before the situation will be normal again,” Megir said.

Another reason to be positive about miner beetles attack is that the damages they inflict are not permanent. From past experience palms like coconut and nipah affected had regenerated and regain full health after the beetles population dissipated.

Presently the symptoms of the beetles’ infestation can be seen on the fronds of nipah and coconut which appeared burnt around the Bako — Sejingkat area in Kuching District .

“The beetle is commonly known as coconut leaf miner, Promecotheca nuciferae (Coleoptera : Hispidae). This particular problem occurred in Samarahan and Kuching District from 1995 to 1997 on a larger scale. It was more serious then, affecting about 28,000 hectares of coconut, nipah and other ornamental palms,” Megir said.

In serious infestations, she said the leaf tips turn brown and curl downwards making the leaves look like they had been scorched by fire.

The entomologist said Nipah was the primary host while the other palms were the secondary hosts. “This pest is indigenous here and it is normally seen as a minor pest of palms.”

Megir agreed with Michael that another possible cause of the infestation could be the destruction of the nipah forest in the area which forced the beetles to migrate to coconut farms to breed.
However, another coconut farmer in Bako who wished to be only known as Kong said the condition seemed to be bad as the whole coconut trees were dying.

“We’ve already sought help from the Agriculture Department; they gave me 10 bottles to hang on coconut trees,” he said. He believed the bottles contained the wasp larvae which when fully grown would be the beetles’ natural enemy.

He said it seemed to work as the coconut trees were becoming better with the leaves returning to green adding that the infestation of his farm started four to five months ago.

“Luckily during the infestation the coconut trees were already bearing fruits,” said Kong and he and his workers were able to pick the fruits thus their income was not totally disrupted.

Local ‘gula apong’ makers who collect nectar from the wild nipah palm are also affected. One of them said her income of RM200 a month from collecting the flower nectar to make the sugary condiment has now diminished.

Sadly for her and her fellow collectors there is no help from the Agriculture Department as the nipah palms are not cultivated and so are not under its purview.

Perhaps the wasps would come to their rescue.