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Erratic Weevil Behavior in Oil Palms Points to Climate Change

Anuradha Raghu

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Weevils that dwell in Indonesia’s oil palm plantations are behaving strangely, and scientists suspect it could be due to climate change.

Weevils that are used by plantations to help pollinate palm trees have become lethargic, showing smaller flight capabilities and pollinating less. Another type of weevil, a tiny beetle variety that typically feeds on coconut and sago palms, has uncustomarily started attacking oil palms.

“It wasn’t like that previously,” said Hari Priwiratama, head of crop protection at the Indonesian Oil Palm Research Institute. “It’s due to climate factors, caused by more extreme weather than usual.”

The change in behavior by these weevils is another blow to farmers in the world’s biggest palm oil producing country, who are already struggling with weaker production in part caused by drier weather. It’s also another example of how climate change, which has been linked to wiping out bees and butterflies in Europe, is impacting nature in sometimes unexpected ways.

The pollinator weevil, originally from Africa, was introduced to Southeast Asia in the 1980s and is known as the most efficient insect pollinator for oil palms. Measuring less than 5 millimeters, these weevils dramatically lift fruit yields by transferring pollen between male and female flowers on the palm tree.

The weevils in Kalimantan plantations in Borneo, which has been hit with more severe dry seasons over the past couple of years and a longer and wetter rainy season, have been flying less than usual and have become less interested in female flowers, Priwiratama said. The inefficient pollination may cause a 15% to 30% reduction in palm oil yields, he said.

Meanwhile, the red-striped palm weevil, which is bigger in size and typically a pest to coconut and sago palms across Indonesia and Malaysia, has started feeding on the insides of oil palm trees, but only in Kalimantan and Papua. The damage from the pest weevils curbs the water and nutrient intake of trees, and risks halving the weight of fruit bunches that are needed to make palm oil.

For now, the attacks account for less than 1% of Indonesia’s total oil palm planted area, but if the industry can’t control this, the threat “will explode in the future,” Priwiratama said. The cause is still undetermined, and further research is needed, he said.

“It’s clear that climate change is contributing to the change in behavior of good weevils,” Priwiratama said. “For bad weevils, maybe there’s indication that climate change is also affecting the behavior and that’s why they’ve become much more aggressive to oil palms. We’re still investigating it.”

Global Phenomenon

Thousands of miles away in Colombia, the world’s fourth largest palm oil producer, farmers are also reeling from the impact of global warming on crops.

The country’s weather whipsawed from severe droughts in 2016 to heavy rains the following year, making the cultivation and irrigation of oil palms more challenging, said Hernan Mauricio Romero, research director at industry consultant Cenipalma. It’s also changing the dynamics of many insects and causing an increase in pests and diseases that’s hurting oil output, he said.

Bud rot disease, a type of plant pathogen that’s destroyed thousands of hectares of oil palm in South America, is now appearing in regions that’s never had it before, Romero, who is also an associate professor at National University of Colombia, said in an interview in Kuala Lumpur.

“Climate change is hitting us pretty badly,” Romero said. “It’s not in the future, it’s happening in the present.”

To contact the reporter on this story: Anuradha Raghu in Kuala Lumpur at araghu3@bloomberg.net

To contact the editors responsible for this story: Anna Kitanaka at akitanaka@bloomberg.net, James Poole

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