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Gypsy moths: The destructive 'experiment gone wrong' causing worry in Minneapolis

They're known to cause millions of dollars of damage to urban trees and forests.
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A neighborhood of Minneapolis is amidst "one of the worst" infestations of the gypsy moth ever seen in Minnesota, and there's good reason why it's causing officials concern.

The Minnesota Department of Agriculture (MDA) implemented a quarantine on the Lowry Hill neighborhood last week, restricting the movement of trees and wood out of the area and requiring residents to inspect their vehicles, equipment and household items before moving out of the area.

It comes after they found trees and outdoor furniture in the neighborhood crawling with caterpillars that will eventually become gypsy moths, and if they're allowed to spread they could potentially cause huge damage to the city's trees and wooded areas.

What do they do?

Check out and the first line will have you thinking you've come across a history book detailing the start of the end of the world.

"Like the tale of the sorcerer’s apprentice, the gypsy moth is an example of an experiment gone horribly wrong," it says, noting the moth was brought to the U.S. in 1869 as part of a "failed attempt to start a silkworm industry."

What it became instead, the website notes, is a "major pest" affecting mainly the northeastern U.S. and southeastern Canada.

The MDA notes they have caused millions of dollars in damage to eastern U.S. forests, as they set about "defoliating" (eating through leaves, basically) large sections of urban and natural forests. They're also found in Wisconsin and are now threatening Minnesota.

They've been a problem in other countries too, with the Japan Times referring to them as "toxic" when in their larval stage. There, they've been responsible for attacking trees including oaks, beeches, chestnuts, Japanese dogwoods and magnolias, among the 300 species it's known to munch on.

"Walking in the woods you could hear their droppings pitter-patter like rain — I kid you not! Park a car under trees and you’d return to find its roof totally spattered with caterpillar poo — which then, with a little rain, will smear and go all gooey," the Japan Times said.

They have a lifespan lasting only months, typically hatching in early spring before moving to the leaves of trees and beginning to eat, mostly at night. They grow by molting – five or six times during their time as caterpillars – and their appetite grows with each molt, notes.

Feeding continues until mid-June/early July before they enter their pupal stage, from which they emerge as a moth. Reproducing and laying eggs until September, at which point they die.

More about the Minneapolis quarantine

The quarantine extends from Mt. Curve Avenue in the north to Franklin Avenue West in the south of Lowry Hill, to Irving Avenue South to the west and Dupont Avenue South in the east.

It's expected to stay in place until early next summer, according to the MDA, with residents asked not to move branches, firewood or outdoor items out of the quarantined area.

An open house will be held at the Kenwood Community Center at 2101 W Franklin Ave. next Tuesday, July 11 to provide more information to residents.

You might have noticed some of the gypsy moth traps the MDA has been setting up in the past several weeks, the department is putting 21,000 of them up on trees, mostly in eastern Minnesota, to identify problem areas for new infestations.

Here's a map of the quarantine area in Minneapolis.

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