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How Do I Stop the Spotted Lanternflies in My Garden?

How Do I Stop the Spotted Lanternfly in My Garden?

“How Do I Stop the Spotted Lanternfly in My Garden?” Question from Tulip Tramp of Wilmington, Delaware

Answer: Oh, you asked the right question. Spotted lanternflies (Lycorma delicatula) first appeared in my garden this year, so I am getting firsthand experience trying to manage them, and they are a nightmare. They are prolific, large, and cluster and suck the juices out of trees in very high numbers–enough to kill. They are lightning-fast, hard-to-kill, and nasty. In my yard, they attack black walnut (Juglans nigra) and willow trees (Salix spp.). They’ve also been hanging out on my dahlias and cardoon. For whatever reason, these fruit-tree pests have yet to attack my peach trees, apple trees, and fig–likely because they favor black walnuts. But, I am also on a quest to lower their numbers and keep them away from my garden.

Spotted Lanternfly Origins

Tree of Heaven is the favorite tree of spotted lanternflies, but they also attack fruit trees, grapes, and black walnuts. (Image by Luis Fernández García)

Spotted lanternflies are highly destructive insects that originate from China, India, and East Asia. Their preferred host is tree-of-heaven (Ailanthus altissima), a Chinese tree that was first brought to the United States in 17 84 and quickly became a common weed tree across much of North America. Tree-of-heaven contains chemicals that make spotted lanternflies bad-tasting and inedible–giving them natural protection from predators that would eat them.

Aggressive spotted lanternflies are newcomers to our shores. They were first discovered in the United States in eastern Pennsylvania in the fall of 2014. Since then, they have taken over areas across Delaware, Maryland, Pennsylvania, New Jersey, and Virginia, where they have caused huge economic damage to the forest, orchard-fruit, and grape industries as well as home landscapes and gardens and the businesses that serve them.

Thankfully, these insects can be somewhat cold-sensitive. “The researchers found that bark temperature of about 14 degrees Fahrenheit is the limit at which the beetle can survive (Frank Kummer, The Philadelphia Inquirer, 2018).” That means they will be limited to regions with milder winters, maybe as cold as USDA Hardiness Zone 5.

Spotted Lanternfly Life Cycle and Management

When you know an insect pest’s life cycle, it provides more knowledge to work with when sorting out ways to kill it. A spotted lanternfly female lays many eggs on branches (or practically anything else when populations are high). One female can lay one or two rows of 30 – 60 eggs. The egg masses are camouflaged with a layer of a protective substance that looks like mud. If you can find the eggs, scrape them off and smash them on sight (see the video below).

The first-hatch, or first-instar, nymphs emerge in May or June, and at this time, they are most vulnerable to pesticides. The nymphs begin to suck at the stems of trees, secreting honeydew as they go. The honeydew then encourages the growth of black mold, another negative side effect of these pests. As the lanternflies grow, they shed their skins and develop new features–including wings. Adults are much harder to kill.

Spotted Lanternfly Management Methods

I favor organic gardening, so I try to work with OMRI Listed pesticides, but spotted lanternflies can be hard to destroy. From what I have read, effective insecticides that are approved for organic gardening include Stoller’s Golden Pest Spray Oil and insecticides containing pyrethroids, among others. These have also been shown to kill nymphs quickly up to the third instar. More powerful insecticides are needed to efficiently kill adults, so it is best to try to kill lanternflies early on.

Initially, I tried to use insecticidal soap on first and second instar nymphs in my yard, but it was not powerful enough to kill them all. Now, I am moving to Safer pyrethrin spray, which is stronger. It should work better. I have also invested in a sprayer that will allow me to target higher tree branches where I see the pests in masses. Pyrethrin spray can also kill beneficial insects and pollinators, so I am just going to target the spotted lanternflies that are on my black walnuts and willows and keep the spray away from any garden flowers. If you can reach them, early instar lanternflies are also easy to kill by just dropping them in soapy water. They cannot swim and die quickly. Hopefully, a combination of these steps will make an impact.

Penn State is also working on a potential bio-insecticide (derived from a native fungus) for lanternflies (click here to learn more). Let’s hope this research will offer an easier, natural way to kill the beasts.

For more information about research and possible management ideas, contact your local extension agent and let them know that you have found lanternflies on your property. Visit U.S. Department of Agriculture (USDA) extension website to find your local agent.

Happy spotted lanternfly hunting. Maybe if we all work to manage them in our yards, we can reduce their populations for the good of all.

Jessie Keith

Black Gold Horticulturist

I also could not resist adding this very clever trap method devised by a very smart teen in my area!

Cultivate Beneficial Insects in the Garden

Ladybug adults and larvae (orange and black) waging war on black aphids!

Your garden is a battlefield with more life and death drama than the Serengeti during wildlife migrations.  Among your beautiful plants and flowers, there is that age-old war playing out every day as the insect world fights over who eats what.  Some insects are pests that eat your plants – they are garden prey.  Other insects are there to eat the plant pests – they are the predators.  Your goal is to provide the perfect environment for predators to thrive to help keep insect pest populations under control.

Where to Find Garden Pests

Whiteflies are common pests consumed by beneficial insects. (Image by Jessie Keith)

New gardeners need to know this: plant pests, such as white flies, aphids and mites,  show up on the weakest plants first.  When a plant’s natural resistance starts to fail, it sends out stress hormones that attract the pests that feed on them, so always study stressed plants to get a real pest assessment. On the upside, stressed plants also produce stress compounds that attract the beneficial insects that consume these pests, which is why it’s smart to hold off on the pesticides.

All too often the response to finding pests on your plants is to spray everything in sight with botanical pesticides to stop the spread.  Sadly, there are often beneficial troops in the field, such as ladybugs, that will get killed, too. Spray should always be a last resort. The best solution is to either give the plant extra care to help it fight off pests. You can also remove badly infested stems or whole plants entirely, to quickly relieve pests from your garden.  This decision is up to you, commander and chief, but identifying your garden’s beneficials will help you get to know them, so you can protect them.

Beneficial Insects

Baby praying mantids are smaller than a fingernail.

Praying mantids:  Easy to spot due to their folded, prayer-like front pincers, praying mantids are large and fearless. These champion bug eaters are a gardener’s palace guard.  They consume a great number of insects, particularly larvae which cause rapid, serious damage.  You’ll find mantid egg cases (which look like they are made of builder’s foam) on bark, stems, fences, and walls, so don’t disturb them.  New mantids will hatch as nymphs; tiny identical copies of their parents.

Ladybug adults are cute, which is why everyone loves them! (Image by Jessie Keith)

Ladybugs:  These are our best bugs for teaching the kids about insect pests and beneficials because ladybugs are cute, not scary. You can always find ladybugs in thriving, insecticide-free gardens. Wherever there are aphids you will find these spotted red beetles and their weird looking larvae. The larvae are the hungriest, eating loads of aphids at a go, but this is also the stage when they are most vulnerable to pyrethrins and other pesticides.

Lacewings:  These delicate transparent insects are voracious feeders that travel from plant to plant gobbling up pests, such as aphids, mites, whiteflies, mealybugs, and thrips.  They’re universally present, like ladybugs, in diverse gardens where there are no chemicals to limit their numbers. Lacewings have long been used for the control of whiteflies in greenhouses, and they do lots of good outdoors too.

Many spider species dwell in the garden.

Garden spiders:  Most folks are naturally afraid of spiders, but in the garden, these predators are at the top of the list when it comes to attacking pests.  There are many types of garden spiders, which cast a wide net to catch prey on the wing or as they move from plant to plant. Even though they may catch the occasional pollinator, they do far more good than damage.

Heavy artillery:  Though not insect predators, the heavy bombers of your garden are birds in the daytime and bats at night.  Bats are vital to consuming tomato hornworm moths, and a single bat can eat up to 600 mosquitoes a night, which benefits everyone.

Quick List of Common Garden Pests

A praying mantid laying in wait for its next meal. (Image by Jessie Keith)

Aphids: These sucking insects attach many flower and vegetable plants, and populations can get out of control fast without the help of beneficials. Their natural predators include ladybugs and lacewings.

Mealybugs: White mealybugs crawl along plant stems and leaves sucking out their juices and doing a lot of damage fast. They particularly like stem crevices. Natural predators include ladybugs, lacewings, and the mealybug destroyer (Cryptolaemus montrouzieri).

Spider Mites: Tiny spider mites populate quickly and suck juices from below the leaves of plants. The beetles and larvae of the all-black spider mite destroyer ladybug (Stethorus picipes) will do serious damage to populations. Standard ladybugs will also eat them.

Thrips: These tiny sucking insects damage the leaves and flowers of many garden plants. Ladybugs and lacewings are two of their biggest natural predators.

Whiteflies: Ladybugs and lacewings will attack the clouds of small whiteflies that feed on the leaves of many garden flowers and veggies.

Leafhoppers: Fast-moving leafhoppers suck the juices from plant leaves and spread viral diseases along the way. Ladybugs and lacewings will help keep them under control.

Assorted larvae: The larvae of many pesky beetles and moths will chew on lots of favorite garden vegetables and flowers. Predators include praying mantids, lacewings, and ladybugs. Birds and bats will also feed on them.

Building Insect Armies

Tomato hornworms are large enough for a praying mantid to devour.

Your first protective step should be to give your plants good care to keep them strong and vigorous! Do not draw your sword to kill a fly, as the Korean saying goes.  Build your armies instead by tending your plants. Use quality Black Gold potting soil and amendments to help keep plants vigorous and further support the age-old secret war of the garden.  Manage pest populations naturally, by removing badly infested stems and plants. Do this and you’ve become a partner of your garden predator protectors who will return the favor, just as beloved watchdogs protect homes at night.