If you have been searching for natural ways to deal with spotted lanternflies, you have probably stumbled across a strange rumor. The question “does milkweed kill lanternflies” is popping up in gardening groups and pest control forums everywhere. The short answer is yes, milkweed can kill lanternflies, but the reality of using it is far more complicated than just planting a few flowers in your yard.
Milkweed contains cardenolides, which are toxic compounds that disrupt the heart function of many insects. For a spotted lanternfly, ingesting this sap is often lethal. However, the method of delivery matters, and the ecological cost of using this plant as a weapon is steep.
Before you rush outside to crush leaves onto every bug you see, you need to understand how this works. You also need to know why many entomologists advise against using milkweed as your primary control method. Let’s break down the science, the practical application, and the hidden dangers.
Does Milkweed Kill Lanternflies
Yes, the toxic sap inside milkweed is deadly to spotted lanternflies. The lanternfly is a piercing-sucking insect, meaning it inserts its mouthparts into plant tissue to drink the fluids. When it feeds on milkweed, it ingests the cardenolides. These toxins bind to the sodium-potassium pump in the lanternfly’s cells, causing heart arrhythmia and eventual paralysis.
This is not a slow death. In most cases, a lanternfly that feeds on milkweed will die within 24 to 48 hours. The effect is most potent when the lanternfly is in its nymph stage, as they are more sensitive to the toxins. Adult lanternflies are larger and can sometimes survive a small dose, but a sustained feeding session will kill them.
However, there is a catch. Spotted lanternflies are not stupid. They can detect the toxic compounds in milkweed before they commit to feeding. If they have other food sources available, they will simply avoid the milkweed. This means that planting milkweed in your garden is not a guaranteed trap. It only works if the lanternflies have no other choice or if you force them to contact the sap.
The Difference Between Contact And Ingestion
You will often see videos online of people squashing lanternflies with milkweed stems. This is a contact method. When you crush the stem and smear the sap on the insect, the toxin is absorbed through the exoskeleton. This is actually more effective than waiting for them to feed.
The exoskeleton of a lanternfly is thin enough that the cardenolides can penetrate it. This causes immediate distress and death within a few hours. It is a brutal but effective method. The downside is that you have to physically catch each bug and smear it. This is not practical for a large infestation.
If you are dealing with hundreds of lanternflies, you cannot chase them all down with a milkweed stalk. You need a broader solution, which is where the ecological trade-offs come into play.
The Ecological Trade-Offs Of Using Milkweed
Milkweed is the only host plant for monarch butterflies. This is the most critical fact you need to consider. Monarch caterpillars rely exclusively on milkweed for food. If you start cutting down milkweed or using it to smear bugs, you are directly harming the monarch population.
Monarch butterfly populations have declined by over 80% in the last two decades. Habitat loss is the primary driver. If every gardener starts using milkweed as a pesticide, we will lose the monarchs entirely. This is not an exaggeration.
Furthermore, milkweed is a vital nectar source for bees, wasps, and other pollinators. When you crush the stems, you are destroying the plant’s ability to flower. This removes a food source for beneficial insects during a critical time of year.
There is also the issue of the lanternfly’s saliva. When a lanternfly feeds on milkweed, it does not just drink the sap. It injects saliva into the plant. This saliva can introduce pathogens that harm the milkweed. You might end up killing your milkweed plants in the process of trying to kill the lanternflies.
Why You Should Not Plant Milkweed Near Grapevines
Spotted lanternflies are attracted to the tree of heaven, but they also love grapevines. If you have a vineyard or grapevines in your yard, planting milkweed nearby is a bad idea. The lanternflies will still prefer the grapes. The milkweed will not deter them from the grapes.
In fact, the presence of milkweed might confuse the situation. The lanternflies will feed on the grapes, which are not toxic to them. They will only move to the milkweed if the grape supply is exhausted. By then, the damage to your vines is already done.
If you want to use milkweed, you must isolate it far away from your valuable plants. You also need to be prepared to sacrifice the milkweed, as the lanternflies will likely damage it before they die.
Practical Methods To Use Milkweed Safely
If you are determined to use milkweed as a control method, you need to do it in a way that minimizes harm to the ecosystem. Here are the steps you should follow.
- Identify the milkweed species. Common milkweed is the most toxic, but butterfly weed is also effective. Do not use tropical milkweed, as it is invasive in many areas.
- Wear gloves. The sap can cause skin irritation in humans, especially if you are allergic to latex.
- Cut a fresh stem from the plant. The sap is most potent when the plant is actively growing.
- Crush the stem slightly to expose the milky sap.
- Apply the sap directly to the lanternfly’s body. Focus on the underside of the abdomen, where the exoskeleton is thinnest.
- Dispose of the crushed stem in a sealed bag. Do not compost it, as the toxins can leach into the soil.
This method is best for small infestations. If you have a large swarm, you will spend hours doing this. You are better off using a shop vac or a sticky trap.
Creating A Milkweed Spray Solution
Some gardeners make a spray by boiling milkweed leaves and stems in water. This creates a concentrated solution of cardenolides. You can then spray this directly on lanternflies or on plants you want to protect.
To make this spray, you need to chop up a large amount of milkweed. Place it in a pot, cover it with water, and boil for 30 minutes. Strain the liquid and let it cool. Pour it into a spray bottle.
This spray is effective, but it is also non-selective. It will kill any insect it touches, including bees and butterflies. You should only use this spray as a spot treatment, not as a general garden spray. Also, the spray degrades quickly in sunlight, so you need to reapply it after rain or heavy dew.
Be careful with this spray. If you get it in your eyes, it can cause severe pain and temporary blindness. Always wear protective eyewear when applying it.
Alternative Control Methods That Are Safer
You do not have to rely on milkweed to control lanternflies. There are several other methods that are more effective and less harmful to the environment.
- Sticky bands: Wrap trees with sticky tape to catch nymphs as they crawl up the trunk. This is highly effective in the spring.
- Shop vac: Suck up adults and nymphs directly. This is the fastest method for large infestations.
- Insecticidal soap: Spray directly on the insects. This suffocates them without harming the plant.
- Neem oil: This disrupts the lanternfly’s feeding and molting cycle. It is safe for beneficial insects when used correctly.
- Remove tree of heaven: This is the lanternfly’s preferred host. Removing it from your property will reduce the population significantly.
These methods are not as dramatic as using milkweed, but they are safer. They also allow you to preserve your milkweed for the monarchs.
The Role Of Natural Predators
Another reason to avoid using milkweed as a pesticide is that it kills the lanternflies before predators can eat them. Birds, spiders, and praying mantises all feed on lanternflies. If you poison the lanternflies with milkweed, the predators that eat them will also die from secondary poisoning.
This creates a cascade effect. You kill the lanternflies, then you kill the birds, then you have no natural pest control left. This is the opposite of what you want.
Instead, let the predators do the work. Encourage birds to visit your yard by providing water and shelter. Do not use broad-spectrum pesticides that kill everything.
Frequently Asked Questions
Can milkweed kill lanternfly eggs?
No. Milkweed sap has no effect on lanternfly eggs. The eggs are protected by a waxy coating that prevents the sap from penetrating. You must scrape the egg masses off surfaces and dispose of them in a sealed bag.
Is milkweed poisonous to pets?
Yes. Milkweed is toxic to dogs and cats. If your pet ingests the leaves or stems, they may experience vomiting, drooling, and heart arrhythmias. Keep pets away from milkweed plants and any crushed stems.
How long does it take for milkweed to kill a lanternfly?
When applied directly to the body, death occurs within 2 to 4 hours. When ingested through feeding, death occurs within 24 to 48 hours. The speed depends on the size of the lanternfly and the amount of sap it absorbs.
Should I plant milkweed to attract lanternflies away from my garden?
No. This is a bad idea. Milkweed will not attract lanternflies away from your garden. They will still prefer grapevines, fruit trees, and maples. Planting milkweed will only add another food source for them to damage.
Does milkweed kill lanternflies instantly?
No, it is not instant. The toxins take time to disrupt the lanternfly’s nervous system. If you are looking for an instant kill, a physical method like squashing or vacuuming is better.
Final Thoughts On Milkweed And Lanternflies
So, does milkweed kill lanternflies? Yes, it absolutely does. The toxins are potent and effective. However, the ecological cost is too high to justify widespread use. You risk killing monarch butterflies, harming beneficial insects, and poisoning the predators that help you control pests.
If you have a small infestation and you have a surplus of milkweed, you can use the contact method sparingly. But for most homeowners, the safer and more effective approach is to use sticky bands, vacuums, and soap sprays. Preserve your milkweed for the monarchs. They need it far more than the lanternflies deserve to die from it.
Remember, the goal is not just to kill lanternflies. The goal is to maintain a healthy, balanced ecosystem in your yard. Using a toxic plant as a weapon might win a small battle, but it will lose the war for your garden’s biodiversity. Choose your methods wisely, and you will have a better outcome in the long run.