Callery pear trees: Why are they ‘worse than murder hornets’?

A callery pear is seen in Johns Creek, Ga. on Sunday, March 13, 2021. A stinky but handsome and widely popular landscape tree has become an aggressive invader, creating dense thickets that overwhelm native plants and bear four-inch spikes that can flatten tractor tires.

Alex Sanz, Associated Press

The tree was first brought to America to save the failing native pear crop a century ago — which it did. Over the years, it has been planted nearly everywhere as a beautiful, hardy and drought-tolerant landscape tree. The Callery pear, with its profusion of white blossoms and two dozen offspring cultivars, was an American hero for a time.

Now it’s an invader, deemed “worse than murder hornets,” in a 2020 U.S. Department of Agriculture webinar that was only half-kidding about the severity of the problem.

Close to a century ago, when the tree arrived on U.S. soil (they are native to China and Vietnam), fire blight fungus was destroying pear crops, according to a 2007 BioScience article about the Callery pear by University of Cincinnati researchers. Experts grafted edible pears onto the imported pears’ roots, resulting in blight-resistant edible pear trees, which saved the crop.

The Associated Press story this week said Callery pear trees “have spawned aggressive invaders, creating thickets that overwhelm native plants and sport nasty four-inch spikes.”

Did we mention that the blossoms stink?

According to AP, “The stench wafting from the tree’s billows of white blossoms has been compared to perfume gone wrong, rotting fish, chlorine, and a cheese sandwich left in a car for a week.”

The most famous of the cultivars is the ornamental Bradford pear, once frequently planted along city streets, which many cities are reportedly now tearing out, while others are banning them.

“They’re a real menace,” Jerrod Carlisle told the Associated Press after discovering that four of his landscape trees and one in a neighboring yard had between them “spawned thousands on 50 acres” that he was converting to woods and wildlife habitat in Otwell, a small community in southern Indiana.

At least 12 Midwestern and Western states are now reporting invasions of Callery pear trees, something that was already a known problem in the South and Northeast, the report said.

Experts from the U.S. Forest Service have described the tree as nearly indestructible. The sprouts have proven quite impervious to burning and mowing, both of which lead to more sprouts. Young seedlings have “spurs that can punch through tractor tires,” according to the Associated Press.

When the tree arrived on U.S. soil, fire blight fungus was destroying pear crops, according to a 2007 BioScience article about the Callery pear. Researchers grafted the edible pears onto the imported pears’ roots and created blight-resistant fruit trees.

Saving birds and butterflies

In Kansas and Missouri, officials are trying to stop invasive Callery pears from “continuing to choke out native flowers, shrubs and trees” in hopes of bringing back wildlife, as KCUR reported.

A single oak in Kansas City can feed more than 400 species of caterpillars before they turn into butterflies and moths, the article said. A wild plum tree is food for close to 300 species; the goldenrod feeds close to 100. The Callery pears are pretty much inedible, so researchers don’t find insects on them. And they’re taking over.

Experts are figuring out how to eradicate the trees. The Missouri Invasive Plant Council said the first option is to cut down the tree, then treat the trunk quickly with an herbicide like Tordon or weedkiller like Roundup. Or you can go after the leaves with those products and cut down the tree after it dies. Wear gloves.

Experts emphasize that those with Callery pear trees need to get rid of them carefully — but it needs to be done. They destroy whole areas nearby. Some states, like Kansas and Missouri, are offering a bonus for taking out a Callery pear in the form of providing a nice, native substitute tree.

Organizations like the Morton Arboretum in Lisle, Illinois, have placed the Callery pear on the not-recommended list.

Callery pear trees: Why are they ‘worse than murder hornets’?
Source: Gabriella Pinoys