Spotted lanternfly: should you pay someone to treat your trees?
Updated · KeystoneProGuide editorial team
What is the spotted lanternfly?
An invasive planthopper from Asia. The Pennsylvania Department of Agriculture says it was first found in the state in Berks County in 2014, and Penn State Extension says that was also its first detection in North America. It feeds on the sap of many plants, with a preference for grapevines, maples, black walnut, birch and willow, and it has since spread to other states. Penn State says it is under quarantine in most Pennsylvania counties.
Does it harm your trees?
Less than its numbers suggest, in most yards. Penn State says that apart from grapevines, tree-of-heaven and black walnut saplings, the spotted lanternfly is not known to kill plants. Its feeding stresses plants and can damage branches locally, and it may add to the long-term weakening of trees already under other stresses. In residential landscapes, Penn State considers it primarily a nuisance pest.
The nuisance is real. Lanternflies excrete a sugary liquid called honeydew, which drips from infested trees, attracts wasps and bees, and grows a black sooty mold. Penn State says that mold stains decks, patios, tree trunks and cars beneath the trees and can be very hard to remove. Lanternflies cannot bite or sting.
When is it active?
There is one generation a year. Penn State says eggs are laid from September to December on trees, decks, houses, outdoor equipment and stones, in masses covered with a mud-like coating; they hatch from late April to June. The young nymphs are black with white spots, the last stage red, black and white. Adults, about an inch long, appear in July and stay active until hard freezes.
Should you treat at all?
Penn State's answer is often no, or not yet. It says the lanternfly cannot be prevented from coming onto any one property, that low numbers may not need treatment, and that not every tree in an infested area needs treating. Its advice is to scout first: watch which plants the insects favor through the season, and consider treatment only if high populations are found and persist.
Two cautions from the same guide shape that decision:
- Treatment does not keep them away. Killing nymphs does not stop more arriving later in the season, and killing adults does not stop more adults arriving.
- Some trees attract them year after year. Adults often gather on a favorite tree for weeks late in the season, and are likely to return to it in later years. Penn State calls those trees good candidates for a systemic treatment, if any is used.
What can you do without a pesticide?
The Department of Agriculture says lanternflies can be controlled by a combination of physical removal at any life stage, removing tree-of-heaven, and pesticides. Penn State's list of non-chemical steps includes:
- destroying egg masses, which it says to look for from fall to summer, including under vehicles and in wheel wells;
- learning to recognize tree-of-heaven, itself invasive, and removing it, since lanternflies thrive on it, though herbicides are often needed to kill it;
- keeping plants healthy, which may reduce the stress of feeding.
Penn State also warns, in its guide, that there are currently no known natural enemies expected to reduce populations significantly.
If you use or hire a treatment, what are the rules?
Penn State says to use the least toxic option that works, only insecticides registered by the EPA or the Department of Agriculture and approved for the site, and to follow the label. It says never to spray any insecticide on plants that are blooming, to protect pollinators.
If you hire someone, the work is a pesticide application on your property, so the company needs a Pennsylvania pesticide business license and the person applying it must be certified or a registered technician. Tree and shrub treatments fall under the ornamental and shade tree category, category 06 in the state's pesticide regulation, rather than the household category. Penn State's guide to choosing a pest management or lawn care company uses the spotted lanternfly as its opening example, and says to verify the applicator's certification card and the business license, and to ask whether there are effective options besides pesticides.
What does the quarantine mean for you?
The quarantine order applies to residents as well as businesses. It prohibits moving any living stage of the insect, and regulates moving things that may carry it, including firewood, landscaping and construction waste, and outdoor household items such as grills, furniture, mowers and tarps. The department says intentionally moving lanternflies is a serious offense. Penn State adds that every business operating in a quarantined county must have a lanternfly permit, which is free, so a company treating your trees should have one.
To see whether your location is in the quarantine zone, use the department's interactive map. Sightings in new areas can be reported online or at 1-888-4BAD-FLY (1-888-422-3359).
For other insects that gather on houses in the fall, see fall invaders, and for the questions to ask any company, see questions to ask.
Sources
- Spotted Lanternfly Management Guide, Penn State Extension
- Spotted Lanternfly, Pennsylvania Department of Agriculture
- Spotted Lanternfly Quarantine and Permitting, Pennsylvania Department of Agriculture
- Choosing a Qualified Pest Management or Lawn Care Company, Penn State Extension
- 7 Pa. Code Chapter 128. Pesticides, Commonwealth of Pennsylvania (Pennsylvania Code)