In 2021, an adult tree in Wadi Hinna, a semi-arid valley in the country’s Dhofar Mountains, collapsed and died. In May 2024 Mr Ali Akaak in Oman sent an urgent message to Dr Venter asking her to visit and see the destruction. One year later, in May 2025, she flew to Oman to see what it was all about.
What she found there was shocking and far worse than she expected. She saw trees that had literally been eaten up by the beetle’s larva and were collapsing under their own weight. She found that already 6% of the trees had died and many had been infected.
Damage caused by larva to stem of baobab
In an article published by Dr Venter and her collegues from Oman, Mr Ali Akaak and Mr Mohammed Akaak, they confirmed that the mango stem-borer (Batocera rufomaculata), was the culprit. They also found that it was the first time any beetle has ever been found to kill adult baobab trees anywhere in the world.
Oman, on the southeastern tip of the Arabian Peninsula and just across the sea from East Africa, is home to a small population of African baobabs introduced over 1500 years ago by traders from Africa.
The mango stem-borer is native to Southeast Asia. Adults live for only two to three months feeding on shoots and bark, but during that time females can lay up to 200 eggs, cutting small slits in tree bark and sealing each egg inside. The grubs or larvae spend almost a year hidden within the wood, tunnelling through the living tissue that carries water and nutrients. As they feed, they weaken and eventually kill their host.
This beetle has long been one of Asia’s most damaging fruit-tree pests. It attacks mango, jackfruit, mulberry and fig trees, often killing mature hosts. It has spread to the Middle East, where it attacks commercial fig plantations.
The very qualities that make baobabs extraordinary survivors in dry climates also make them ideal nurseries for borer beetle larvae. Their water storing, soft trunks and nutrient rich tissue feed and protect larvae for nearly a year until they mature. As the larvae feed, they hollow out the interior of the baobab, leaving the outer bark intact and the infestation hidden, until the stem suddenly collapses.
When the first deaths were recorded, Oman’s Environment Authority launched an emergency control programme with help from local communities and researchers.
Mango stem borer – Batocera rufomaculata
Infested trees were treated with systemic insecticides, larvae were manually removed from trunks, and light traps were set to attract and kill adult beetles at night. Tree stems were also coated with agricultural lime and fungicide to deter further egg-laying.
These actions seem to have slowed the outbreak, but they are labour-intensive and feasible only for a small area. Across a continent, such methods would be impossible to maintain.
In Asia, scientists have identified natural enemies of the mango stem-borer, including parasitic mites and nematodes, which could form the basis of a long-term biological control strategy. Researchers now urge that such approaches be developed as a matter or priority before infestations cross into Africa.
The mango stem-borer is highly mobile. Adult beetles can fly up to 14 kilometres in a single night, and global trade makes it easy for insects to cross borders unnoticed, hidden in plants and ornamentals destined for the agriculture and garden sector.
If the mango stem-borer was to reach mainland Africa where the baobab is considered a keystone species, it could devastate both ecosystems and livelihoods. While not yet recorded here yet, it occurs on nearby islands such as Madagascar, Réunion and Mauritius. This means there is still time to act.
Early detection and prevention are far cheaper, and far more effective, than trying to stop an outbreak once it begins. Stronger biosecurity measures at African ports and borders, particularly for shipments of wood and live plants are required. Collaboration between research institutions, agricultural departments and the baobab industry will also help: sharing data, testing biological controls and establishing monitoring systems before further outbreaks occur.
The death of baobabs in Oman is more than a localised problem. It’s a warning of what could happen elsewhere if the beetle spreads unchecked.
But it also offers a chance to prepare. If African countries act now, tightening biosecurity, supporting research and raising awareness, they can protect one of the continent’s most iconic and life-sustaining trees before this threat ever reaches our shores.
Huge thanks to Skoon, Milbon and Unrooted Drinks for supporting this important research.
