Ruling the roost in estates

This is written by my colleague at New Sunday Times.

Owls have been associated with wisdom and bad luck. But some oil palm plantations have been providing lodging for these predatory birds to act as rodent catchers since the 1980s, writes SUZANNA PILLAY.

AS far as sustainable farming goes, some practices are something to hoot about. For 30 years, Sime Darby (SD) Plantation has successfully run a Barn Owl programme in its estates.

“Today, there are owls in our estates in Malaysia, except for Sarawak, as well as some of our operations in Indonesia. The number of owls are estimated at around 21,000 birds in Peninsular Malaysia alone. 

"Work is in progress for us to bring the owls to our estates in Sarawak, and later in Liberia,” said SD’s head of research and development Dr Mohamed Nazeeb Ali Thambi on a visit to its oil palm estates on Carey Island and Jomalina refinery.

SD Plantation first started to consider the viability of barn owls as a sustainable and environmentally friendly method of pest control on its oil palm plantations in the early 1980s, when commercial-scale trials proved their effectiveness in the biological control of rats.

According to Nazeeb, commercial-scale implementation at SD’s oil palm plantations commenced in 1987.

“There was no purchase, or training of the owls. All we did was to set up nesting boxes for them and the population naturally increased. They occupied the nest boxes erected at the estates and will continue to do so as long as there are rats available as a food source.”

Biannual census is conducted to ascertain the population of barn owls in the estates, he added. The ratio of owls per estate is worked out based on the occupancy rate per box and the territorial range of the owls.

“Usually, there will be a pair of adult owls occupying a box for every 10 hectares of an estate. There are two breeding seasons — July to October, and November to February. The eggs hatch after 32 days. The chicks will remain in their nests until they can feed on their own after about eight to nine weeks, when they fly out of their nests and live on their own as adults.”

He said with the use of barn owls, the oil palm plantations are able to reduce rat control costs by 30 to 40 per cent. A barn owl eats an average of one rat per day. A family that comprises two adults and two baby birds could consume 1,200 rats per year.”

It has been estimated that rats consume up to six per cent of crop production each year. In severe cases, the losses can be higher.

“To maintain the prey-predator equilibrium and keep the damage caused by rats below the economic threshold, we still need some chemical intervention, albeit, in a much smaller quantity compared with when barn owls are not used.”

Aside from rats, Nazeeb said leaf-eating insects, like bagworms, nettle caterpillars, rhinoceros beetles and termites, also cause damage at oil palm estates.

Oil palm planters grow the beneficial turnera subulata to give
shelter to bigger insects that feed on bagworms, nettle
caterpillars, rhinoceros beetles and termites.
“Encouraging the presence of more beneficial predatory insects, parasitoids and entomo-fungi help eliminate leaf defoliating insects in oil palm estates, while cultivating beneficial plants and flowers that provide shelter and supplementary food like nectar will encourage the population of predators and parasites.”

Crop losses caused by such insects can be very devastating, he said. He cited leaf-eating caterpillars, which are able to strip the leaves of the palm resulting in crop losses over a period of two years following an infestation.

Another common oil palm pest, rhinoceros beetles bore into the cluster of developing spears in the crown of the palm to feed on the soft tissues. They could also bore through the frond bases into the soft tissues of young, unopened leaves. The damage caused by rhinoceros beetles will result in crop losses upon maturity.

Pests like termites attack oil palm trees by damaging the meristem in the crown and feed on the living tissue in the trunk, eventually killing the tree. Using direct bio-control agents, such as viruses and fungi to infect the pests, at oil palm estates is also a must,” he said.

Rhinoceros beetles can be killed using entomopathogenic (parasitic) fungi. The fungi’s spores penetrate the beetles’ cell tissue and secrete toxins. Entomopathogenic fungi are also used to control termites, but this method is still a work in progress for commercial use.

Pheromone trapping is efficient in controlling the population of flying insects, like rhinoceros beetles, which would otherwise require fortnightly spraying of insecticides in plantations.

“Spraying is costly and labour intensive. The pheromone attracts the beetles and traps them inside a bucket, where they will eventually die. These methods were introduced in the 1960s and, suffice to say, there have been significant savings in terms of cost as well as the improvement of our yield.”

In an outbreak of pests, where natural enemy pressure is no longer sufficient, environmentally friendly insecticides will be used until the situation is under control.

“An outbreak is deemed to have occurred when damage can be seen very clearly on leaves and pest counts have gone up above the defined threshold. Normally, one or two rounds of insecticide will bring back equilibrium. The estates practice an alert and survey system to monitor pest levels so that early intervention is possible with minimal use of insecticides.”

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