RIYADH: The acacia tree is of significant importance to both the environment and culture in Saudi Arabia. It provides shelter for migratory birds and protects travelers and Bedouins in the Arabian Peninsula’s hot desert.
Among the many environmental benefits of the acacia tree is its ability to prevent desertification; its roots improve soil fertility; it provides shade and lower temperatures; it stores carbon and reduces carbon dioxide levels; and it stabilizes dunes in desert areas.
An invasive beetle — scientific name Agrilus planipennis fairmaire — has been attacking trees for years, killing many of them in the Kingdom, including perennial trees.
The 'Emerald ash borer' (scientific name: Agrilus planipennis Fairmaire) is a highly destructive wood-boring beetle feeding on the phloem of ash trees. (Supplied)
Oubaid Alouni, an environmental consultant and former consultant at the National Center for Vegetation Cover Development and Combating Desertification, explained the role of the acacia tree in the ecosystem and how the pest threatens its existence.
He outlined the different types of acacia trees in Saudi Arabia.
“The acacia tree grows naturally in the desert. It is a desert umbrella tree and is divided into two types; the Iraqi acacia and the Najdi acacia, and reaches around 55 types in total,” Alouni said.
There is also another type of acacia tree that grows in Asir, locally known as Al-Kanhbal, scientific name Vachellia origena, that differs from the Najdi acacia, which has long branches and provides ample shade.
While some acacia trees are native to Saudi Arabia, others were imported, such as acacia raddiana. They all share a similar trait, providing vital protection from strong sunlight.
While some acacia trees are native to Saudi Arabia, while others were imported, along with the wood borer. (SPA file photo)
“Any hiker, any traveler, who wants to go to the desert must pass by this tree and take shelter under it,” Alouni said, describing how people have always been connected to this species and valued it.
Securing native trees, not only acacia, holds a deeper meaning for the culture and tradition, he said, such as when the Prophet Muhammad used to sit under the Ziziphus spina-christi.
The acacia tree is threatened by the Agrilus planipennis Fairmaire as this species relies on the tree for nutrients.
“This insect reached Saudi Arabia through imported wood, as they found larvae inside wood imported from Russia,” Alouni said.
DID YOU KNOW?
• Some of the finest honey in the Kingdom is produced from acacia and jujube trees.
• Acacia trees help reduce sand encroachment in the desert and provide shelter for several bird species.
• The acacia tree can withstand drought for up to 10 years, even severe drought.
The pest is a highly destructive wood-boring beetle feeding on the phloem of ash trees. It is also known as the Emerald ash borer, and is native to China, Japan, South Korea, Mongolia and Russia.
This bug is typically a small, metallic green beetle, around half an inch (about 1.2 to 1.5 cm in length), and one of its distinguishing features is that when the wing covers are lifted, the upper abdomen is bright red.
Its life cycle involves multiple stages. The first is the egg stage, during which females lay 40-53 eggs.
The larva lives inside the tree for one to two years, eating the layer between the bark and the main trunk. (Supplied)
Then comes the larva, the longest stage of the beetle’s life cycle, lasting almost a year.
“The larva lives inside the tree for one to two years, eating the layer between the bark and the main trunk,” Alouni said.
After that, it goes through a shorter stage, as a pupae, that lasts about 20 days.
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Finally, it reaches the adult stage and is known for chewing through the wood and emerging from trees, forming a small, D-shaped exit hole about 3 to 4 mm wide. This stage of its life is usually short, lasting about 20 days.
The pest is now attacking olive trees in the US, Alouni said.
“In Ohio, I believe, it has begun to invade olive trees terrifyingly. This insect is very dangerous.”
The life cycle of Agrilus planipennis Fairmaire involves multiple stages before reaching adulthood. The first stage is the egg stage, during which females lay 40-53 eggs. (Supplied)
Among the factors that enabled this insect population to increase nationwide is the hunting of birds, especially migratory birds, because they usually feed on insects.
However, the biggest threat to the ecosystem is ignorance, Alouni said, as many people believe the insect is part of the Kingdom’s native environment and that protecting it contributes to a balanced ecosystem.
“There are still people who say, ‘Leave it alone; it’s part of the ecological balance,’ which is, of course, incorrect. This insect is an invasive species in our environment,” he said.
Oubaid Alouni, an environmental consultant and former consultant at the National Center for Vegetation Cover Development and Combating Desertification. (Supplied)
He also believes that pruning trees leaves branches exposed and vulnerable to this insect entering the tree, and that transferring wood from one location to another may provide an opportunity for the larva to expand and increase its numbers.
To address this environmental issue, Alouni told Arab News about the efforts being made to safeguard and protect the Kingdom’s natural treasures, including organizing discussions and workshops to explore the issue and exchange potential solutions among experts.
Also, he believes that a particular bird species, the woodpecker, is one of the most effective ways to reduce the numbers of the beetle.
The pest is a highly destructive wood-boring beetle feeding on the phloem of ash trees. (Supplied)
“It’s called the Arabian woodpecker, yet it only exists in Asir and in small populations, too,” he said.
According to Alouni, the Arabian woodpecker hears the insect inside the tree, hits the branch with its beak and removes it.
Arabian woodpecker. (James Eaton photo / via Wikimedia Commons)
One of the strongest methods to contain pests is biological control, which uses other species to help the ecosystem naturally protect and restore its balance.
One animal feeds on another to keep the environment balanced, such as using Orussidae — a parasitic wood wasp — or placing large numbers of chickens and other birds in forests and farms.
The Orussidae or the parasitic wood wasps, along with birds, are better alternatives to harmful pesticides in fighting the destructive beetle. (Wikimedia Commons)
“It is called Orussidae in the United States … it kills insects very fast.”
Chemical methods can also be used, but Alouni does not endorse these due to their environmental risks.
