Botanic gardens forced to make harrowing decision after pest infests ancient trees

Twenty trees will be felled at Perth's Kings Park to try and stop an invasive borer spreading to other rare plants.

A rapidly spreading insect outbreak has infested trees in a world-renowned botanic garden. Discovery of the invasive pests has forced local authorities to make the heartbreaking decision to fell 20 trees in the Australian park to try and protect other plants in its rare and endangered flora collection.

Over 80 suburbs across Perth have been impacted by the Polyphagous shot-hole borer since it was first detected late in 2021. Some of the trees are understood to have stood for 120 years in the 400-hectare Kings Park which overlooks the city’s central business district.

Luckily most Australian trees are less susceptible to the borer and they make up the majority of trees in the park. “The infested trees being removed from Mounts Bay Gardens in Kings Park include Moreton Bay Figs, Port Jackson Figs and Coral Trees,” the Botanic Gardens and Parks Authority (BGPA), which manages the site, told Yahoo News Australia.

A large Moreton Bay Fig in the Mounts Bay Gardens at Kings Park.
Large trees including Moreton Bay Figs will be destroyed in Mounts Bay Gardens in Kings Park. Source: BGPA

A supplied image shows one of the tiny creatures dwarfed by a five cent coin, while another shows its bore holes are around the size of the end of a pen. The borers are native to South East Asia and slowly kill trees by creating multiple entrance holes in trunks and branches.

A quarantine area has been established around most of metropolitan Perth and a Department of Primary Industries campaign encourages residents to report any sightings of the pest. Over 59,000 properties have now been inspected and trees have been pruned and felled to contain the problem.

BGPA said it is working closely with the department to respond and detect the borers across the sites it manages. “Surveillance work is continuing in association with DPIRD, and a number of (borer) traps are in place and monitored throughout Kings Park,” it added.

Authorities struggling to combat invasive pests

Across Australia, authorities appear unable to stop the spread of several invasive insect species. Advocacy groups like the Invasive Species Council have urged state and federal governments to do more to strengthen the nation’s biosecurity.

Left - a five cent coin next to a borer. Right - Several borer holes next to a pen.
The 2mm long borers have infested trees in 80 Perth suburbs. Source: DPIRD

The varroa mite has spread rapidly across NSW, threatening honey bee hives, since it was discovered at a Newcastle port in 2022.

Meanwhile Queensland and Commonwealth authorities have failed to stop the invasion of fire ants which have been described as a "global super pest" and are on the verge of becoming an established pest species in Australia.

In Tasmania, a small colony of China fir borers was discovered inside a bed bought at Harvey Norman in 2023, although action taken by the customer prevented them from escaping into the wild. The retailer did not respond to questions about the incident at the time.

But it’s not just insects that have authorities worried. Last week, Victoria issued a priority pest alert after an Asian black-spined toad was discovered in Melbourne. Images have recently been circulated online, showing the proliferation of the cane toad in Queensland, which has rapidly spread since its introduction in the 1930s.

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