Science

Insect-killing plant found by Australian highway is new to science

tobacco plant

Nicotiana insecticida, a newly described tobacco plant that kills insects

Maarten Christenhusz

A newly described species of wild tobacco that scientists found growing next to a highway truck stop in Western Australia is covered in sticky glands that trap and kill small insects, including gnats, aphids and flies.

While a range of carnivorous plants are known across the plant kingdom, this is the first wild tobacco plant discovered to kill insects. Dubbed Nicotiana insecticida, it was uncovered by a project looking for tobacco plants across Australia.

The team, which included Mark Chase of London’s Royal Botanic Gardens, Kew, collected seeds from the insecticidal plant at a truck stop on the Northwest Coastal Highway, and then cultivated them at Kew, where the plants went on to develop the same sticky glandular hairs and to kill insects inside the greenhouses.

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The insect-ensnaring hairs resemble those on carnivorous sundew plants, but it isn’t clear if the plant extracts any food from the insects it kills. “We have no evidence that there is any nutritional benefit to the plant,” says Chase, who adds that the team is arranging some tests to see whether the plant absorbs any nutrients.

But even if it doesn’t absorb nutrients, killing insects in this way could still be beneficial for N. insecticida. “It definitely protects the plants from insects like aphids,” says Chase.

The plants may also benefit when the dead insects decay. Chase says the species may be like South African Roridula plants, which kill insects in the same way. “There is a bug that lives on these plants and is not trapped by the sticky hairs. It eats the trapped insects and defecates on the ground, and the plant benefits from this,” says Chase. However, there is no evidence yet that this is what happens with N. insecticida.

tobacco plant

Nicotina insecticida has sticky hairs that trap insects

Maarten Christenhusz

The plant hasn’t yet been approved for commercial use by Australia, and the terms of the collecting permits issued to botanists like Chase strictly prohibit them from developing commercial applications. However, Chase says N. insecticida is fairly easy to grow and could perhaps be used as a biological control agent for killing aphids and fungus gnats in greenhouses.

The species is one of seven new-to-science species of Nicotiana described by the team. The others include Nicotiana salina, which grows along salt lakes on the eastern edge of the Western Australian wheatbelt, and Nicotiana walpa in the Uluru-Kata Tjuta National Park in the Northern Territory, which only grows after storms strike the desert.

It has been a busy week for insecticidal plants – a study published on Monday revealed that a plant that grows in bogs along the west coast of North America uses its flowers to eat insects. Before now, researchers had no idea that Triantha occidentalis was carnivorous.

Journal reference: Curtis’s Botanical Magazine, DOI: 10.1111/curt.12402

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