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Growing Green: Stopping Spotted Lanterfly

It unfortunately was a productive Summer of 2019 for the Spotted Lanternfly (SLF), an invasive pest present in Pennsylvania and some other eastern states.

The SLF threatens grape production, tree health and can damage high-value ornamentals in home landscapes.

At stake are Pennsylvania’s grape, tree-fruit, hardwood, nursery and landscape businesses, which generate agricultural crops and forest products worth nearly $18 billion annually.

Native to parts of Asia, the SLF was identified for the first time in the United States in Hereford, Berks County, in 2014.

To slow or stop the spread of SLF, the Pennsylvania Department of Agriculture imposed a quarantine regulating the movement of plants, plant-based materials and outdoor household items out of the quarantine area.

These areas are, as of the publication date of this column, the counties of Berks, Bucks, Carbon, Chester, Dauphin, Delaware, Lancaster, Lebanon, Lehigh, Monroe, Montgomery, Northampton, Philadelphia and Schuylkill.

Residents living in infested areas are using a variety of methods to control SLF, including destroying egg masses, trapping them with sticky bands, eliminating one of their favorite host trees and using insecticides. SLF are particularly attracted to the Tree-of-Heaven.

The SLF uses piercing-sucking mouthparts to feed on sap in trunks, branches, twigs and leaves. The oozing wounds leave a greyish or black trail on bark.

As it digests the sap, the insect excretes a substance known as honeydew that, along with sap from the weeping wounds, can attract bees and other insects.

The honeydew and sap provide a medium for growth of fungi, such as sooty mold, which can cover leaf surfaces and stunt growth. Plants with heavy infestations may not survive.

The Pennsylvania Department of Agriculture requires residents to act to control SLF.

Property owners should choose the least toxic management method that works.

Many people are fearful of SLF and worry the bugs may affect the health of their trees.

Based on observations in previous years since the infestation was first reported in 2014 in the region, it is believed that a few SLF feeding on a large, healthy tree are unlikely to cause permanent damage.

On the other hand, thousands of SLF might weaken a tree. To date, no one has quantified how many SLF will harm a tree or how badly the tree will be affected.

Consider destroying SLF on individual trees by trapping or swatting them instead of using a lot of insecticides.

If you decide to use an insecticide to kill SLF, there are some important safety measures and pesticide rules to follow. Before using any pesticide product, always read the label and be informed to be safe.

Only use registered insecticides to kill SLF. Recipes for homemade sprays made from cleaning, automotive, cooking or other household products might be more harmful to the environment or to plants.

Insecticides registered with the Environmental Protection Agency have been tested for safety and efficacy. The label includes important information, including directions for safe mixing and use and precautions to protect pollinators and the environment.

In Pennsylvania, the tree or plant on which you plan to use an insecticide must be listed on the product label.

For example, if you want to spray an insecticide on an ornamental tree to kill SLF, the product label has to state that it is registered for use on ornamental trees.

If you want to spray an insecticide on a grapevine to kill SLF, the product label has to state that it is registered for use on grapes.

In Pennsylvania, the insecticide does not have to list SLF on the label in order to use it legally, but the tree or plant where it can be used must be listed on the label.

Read the label and follow directions. Plan to spend time reading the label. You can find labels for insecticides online and you can read them before you buy an insecticide.

Read the label, figure out how much of the product you will need and you will know how much you need to buy.

It’s important to protect pollinators. Avoid spraying plants that are flowering or are about to flower. Follow directions on the label to protect pollinators and other beneficial insects. Also, protect streams, wetlands and water sources. Be careful when using insecticides so they do not contaminate water resources or harm aquatic creatures. Follow label directions to be safe.

Avoid using the same insecticide all the time. Some insects have developed resistance to specific insecticides that have been used repeatedly to kill them. When this happens, that insecticide has little effect on the insect. Researchers have not seen resistance occur in SLF yet, but it is best to rotate between different groups of insecticides to reduce that risk.

Choose the least toxic insecticide that is effective. Results from scientific experiments have been compiled into lists of effective insecticides for home gardeners, landscape professionals and commercial fruit and grape growers. Experiments are being conducted to test additional insecticides for their usefulness against SLF.

Universities such as Penn State, Kutztown, University of Pennsylvania, Temple, Rutgers, University of Delaware, and others are working on projects related to Spotted Lanternfly control, non-target impacts, biology, and economic impact.

Information on the Spotted Lanternfly and erradication:


“Growing Green” is by Lehigh County Extension Office Staff and Master Gardeners. Lehigh County Office, 610-391-9840; Northampton Office, 610-813-6613.

CONTRIBUTED PHOTO BY EMELIE SWACKHAMERA swarm of Spotted Lanterflies on the bark of a tree.