Roots and Shoots: How Bad Is That Bug, Really?

For weeks I’ve been fielding texts and calls about the gardener’s apocalypse of spongy moth caterpillars and maple seedlings. Mass quantities of pretty much any species freaks people out, and I’ve been talking friends and clients down from reaching for pesticides and herbicides. 

My worst fear is that harmful chemicals are deployed against threats that aren’t really threats at all. As reported in The Current last week, research shows that trees don’t suffer long-term damage from spongy moth caterpillars. While maple seedlings are a nuisance in the lawn, they don’t survive mowing and can easily be pulled from flower beds while they are small, or repeatedly cut down if they develop stronger roots. 

With this in mind, I jumped at the chance to learn, during a Cornell presentation, more about the spotted lanternfly, another insect that inspires panic and certainly unnecessary pesticide use. 

When the spotted lanternfly was first reported in New York in 2020, there was justifiable fear about its impact on forests. Native to Asia and first documented in the U.S. in 2014 in Pennsylvania, the brightly colored insect sucks the sap from trees and plants, reducing available starches and sugars. 

Fortunately, the insect’s feeding has been shown to be negligible on trees, which is very good news. While the sight of a maple trunk covered in sap-sucking insects is alarming and gross, they aren’t doing long-term damage. 

There’s still cause for concern, though. The agricultural impacts have been greater than the forest impacts. So far, the spotted lanternfly has been known to feed on more than 100 types of plants and trees. Its Top 5 species are ailanthus (aka tree of heaven), black walnut, willow, red maple and grapes. 

With nearly 500 wineries in New York, grape growers are especially vulnerable. The lanternfly feed in swarms and have decimated vineyards in a single season. As the insect’s population continues to increase here, Hudson Valley growers are on alert to monitor closely and try to control outbreaks. 

The instars, which hatched recently, are small black bugs with white polka dots. They can’t fly and feed on vegetables. Cucumbers seem to be a favorite, along with squash and cantaloupe. 

The action items here are to take caution when it comes to preventing the spotted lanternfly from moving into new territory. It’s amazingly good at hitchhiking because it is able to lay eggs on any type of surface — rock, wood, fabric, plastic, metal and rubber, as in tires. 

It can stow away on your car in the crevice of the trunk, or in the trunk or wheel well. Then we unknowingly give it a lift to another location. 

With this superpower, it has spread through 23 counties in New York and 15 states, as far away as Indiana and Tennessee, with the aid of humans. Learning to identify the egg masses, checking equipment like chairs and tents that you move from place to place, and knowing how to remove and kill the egg masses all will help reduce its spread. 

Then there is the issue with the tree of heaven, a difficult-to-manage species that spreads rapidly and can’t be cut down without making the problem worse. Tree of heaven and the lanternfly are ecosystem friends. It is the top species the insect feeds on, and having it in your yard increases the likelihood of having lanternflies. 

If you come upon a cluster of trees of heaven (there is never just one), they are sharing the same root structure. Cutting it down provokes the tree into sending up dozens of new shoots from the connected root. You might have started with five and now there could be 20 to deal with. 

It also grows quickly, up to 8 feet in a season, reaching up to 100 feet at maturity. It’s a high priority for invasive species management, and more of a threat to forests than the spotted lanternfly. 

For more information, Cornell’s website has identification and management tools about the spotted lanternfly (bit.ly/cornell-lanternfly) and the Penn State Extension has a comprehensive guide about ailanthus control (bit.ly/psu-tree-of-heaven).