Missouri turns to imported weevils to kill invasive plant

KANSAS CITY — An alien plant species has invaded Missouri and is threatening to overrun crops and livestock pastures.

To combat the scourge weed, officials are deliberately releasing two alien insect species to destroy its roots and seeds.

What could possibly go wrong?

History shows that bioengineering projects can have unintended consequences. But agronomists and entomologists say there’s nothing to worry about here.

The root weevil and the flower head weevil being introduced in Missouri will feed only on the noxious spotted knapweed plant, they say, and even if the alien insects reproduce into the millions, they will not disrupt the ecology, except in ways that we want them to.

“They are not going to become pests in themselves,” said Ben Puttler, professor emeritus of entomology at the University of Missouri.

However safe the knapweed weevils may be, the record of deploying one species against another is spotted with repercussions that often are not understood for years or even decades. Some alien species can end up attacking native plants or disrupting the food chain in complicated ways:

But there are many cases in which biocontrol of pests has been successful without side effects, going back to the 1880s, when an Australian beetle was released to combat a pest afflicting California citrus crops.

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