8 Simple Ways To Get Rid Of Leaf Beetle Larvae

The Lily Leaf Beetle is a European invasive insect that was first found in North America in the 1940s. This pesky insect can devastate the garden and should be controlled as soon as it’s found. Many gardeners want to avoid harsh insecticides that are harmful not just to the target insect, but to all of the beneficial insects as well.

The most effective means of leaf beetle eradication is to physically remove adults, eggs, and larvae from your plants by hand. Neem oil, Castile soap, natural predator insects, and simply maintaining plant and insect diversity are also effective in controlling leaf beetle infestations.

These beetles and their larvae can be extremely difficult to remove once established even though the removal methods are quite simple – so we recommend always contacting a professional if you’re unsure or the infestation is quite large. However, after you do that, follow along to discover 8 tips for getting rid of leaf beetle larvae!

Where Do Leaf Beetles Lay Eggs?

Leaf beetles are present in North America in much of Canada and the U.S. There are many types of leaf beetles, and you can identify Lily Leaf Beetles by their distinctive scarlet red color. Lily leaf beetles, as their name suggests, lay eggs on lilies and related species of plants.

You can identify Lily Leaf Beetle eggs by their red color, which gets darker as the eggs develop.

larvae are born with lighter coloring and engage in a behavior in which they cover themselves in a protective layer of insect droppings, disguising their appearance before they pupate. Check out the image of that above… wild!

These insects have a voracious appetite and can make their way through huge amounts of foliage as they grow and develop. Because they are an invasive species, they lack natural predators in North America, making them extremely difficult to eradicate.

Leaf Beetles Prefer To Lay Eggs On Lilies

According to Utah State University, adult leaf beetles do sometimes feed on plants outside of the lily family. They are commonly found on ornamental plants such as Hostas, Solomon’s Seal, and Hollyhock, and even false lilies such as Daylilies, Canna Lilies, and Calla Lilies. 

Although they will feed on these plants in the absence of lilies, Lily Leaf Beetles will only reproduce on the leaves of true lilies. 

You will likely notice adult leaf beetles before they begin to lay eggs, so this is a good time to begin making an effort to remove them. The adults will emerge from their winter hibernation around the time that lilies begin to put out their foliage. 

If you happen to have a lot of Hostas or Lillies, there’s a good chance you have leaf beetles, and a whole bunch of other insects! Head on over to our article to find a list of bugs that love to eat Hostas!

They Lay Eggs On The Undersides Of Leaves

Once you begin to notice the bright crimson beetles, know that they will begin to reproduce about 2-3 weeks after they emerge, using that period of time to fill up on leaves and find a mate.

Use this timeframe to try to remove as many adults as possible to reduce the number of beetles that are able to reproduce and mark your calendar a couple of weeks out to begin looking for eggs.

A Leaf Beetle’s Eggs Will Be On The Underside Of Leaves

Lily Leaf Beetles lay their eggs on the underside of the lily plant’s foliage, attaching rows of a dozen or more eggs that are yellow-orange in a color that deepens to red.

These eggs will develop for about ten days before the larvae emerge and begin to feast on your precious lily plants. The adults will continue to mate and reproduce throughout the summer, sometimes producing as many as 450 new insects in a season

Sometimes Leaf Beetle Eggs Can Drop Down To The Soil

You will sometimes find these eggs have dropped down into the soil, where the larvae will actually drop down or climb down to the soil to pupate in cocoons before they emerge as mature adults in two to three weeks.

Because of this movement, you will want to make sure to closely inspect the entire lily plant where leaf beetles are present, including the foliage, flowers, and soil, all of which may contain eggs.

Adults also spend winter in the soil near the lily plant, burying themselves beneath the soil, mulch, or leaf debris to protect themselves from the cold.

8 Simple Ways To Get Rid Of Leaf Beetle Larvae

Before you run for the insecticides, let’s run through a few simple tips that you can use to eliminate Lily Leaf Beetles and their larvae from your garden. 

Begin your mitigation efforts in early spring when you start to see the adults emerging from their winter hibernation, around the time your plants begin putting out spring foliage.

Eggs will begin to appear on the undersides of the foliage around April. Turn over leaves to carefully inspect the undersides, where the eggs and young larvae like to hide.

Now that you’ve got them in your site, its time to take some action!

Remove Eggs By Hand (Or Glove)

The most effective method of getting rid of leaf beetles is simply to remove them by hand. This method is not necessarily efficient but eliminates any doubt that the leaf beetles will survive to reproduce. 

Early morning is the best time to begin removing larvae from the undersides of the leaves, but simply plucking them is not enough to eradicate them completely. You can either crush the insects between your fingers (with latex or rubber-lined garden gloves) or bring a jar of soapy water (dish soap or Castile soap is best) and drop the larvae into the jar. 

Spray Them Off With A Hose

If you are particularly squeamish about handling leaf beetles, you can always opt for some other methods that put some distance between you and the slimy larvae. 

One option is to just spray down your plants thoroughly with a hose to knock the larvae off of their leafy buffets. Put your hose on a stronger jet setting, and spray away at the undersides of the leaves.

This method will work best for very young larvae or even eggs. The beetles will have more limited mobility at this young phase and may not be able to climb back up to their food source.

The only drawback to this method is that the adults will remain mobile and can sometimes reproduce multiple times in a season. So, if you are using this method, make sure to check back throughout the spring and summer to make sure you are knocking off the new generations of beetles as they continue to reproduce.

Ladybugs Can Be A Natural Predator To Leaf Beetles

There are very few known predators of Lily Leaf Beetles in the U.S.

Utah State University, outlines some preliminary studies being done on potential biological control techniques including three species of parasitoid wasps from Europe which lay eggs inside of the leaf beetle larvae, using the living hosts for food as well as a tiny mobile home.

Given that it is unlikely you can purchase parasitic European wasps where you live, and we don’t want you to try to, you may want to turn to an effective North American predator insect we all know and love, ladybugs!

Ladybugs are used widely in gardening for organic pest control and are a good option to control populations of leaf beetles as well as other garden pests such as aphids. 

How Do The Ladybugs Help?

To use this method, release the ladybugs early in spring, as the larvae begin to emerge from the eggs, and then just let them handle the rest!

The ladybugs will go to work consuming the invasive larvae while leaving the beneficial insects you like alone. 

It is easy to find and purchase live ladybugs, such as these Bazos Bags that contain 1500 or more ladybugs.

Castile Soap May Work To Remove Leaf Beetles

Soap is a great product to use when hand removing beetles, as we discussed in the first tip, but you can also apply Castile soap directly to the plant to eliminate eggs and larvae.

Castile soap is milder than traditional insecticidal soaps but works in much the same way. It is made up of vegetable oils and glycerin, which helps explain why it is effective pest control.

When applied to the leaves, the soap will cover the eggs and young larvae and will help get rid of them. Castile soap also breaks down the waxes that form a protective layer on the insect, acting as an insecticide.

To use this method, dilute a very small amount of a mild, unscented Castile soap like this Whole Naturals Soap Variety, in water and spray it or wipe it onto the leaves where the eggs and larvae reside.

Dish Soap Can Work Well With Large Leaf Beetle Infestations

If the infestation is particularly bad, you may need to graduate to a more heavy-duty soap. Most commercial insecticidal soaps are actually just a highly refined version of dish soap, according to Clemson University. 

There is some risk to this method because of the number of additives, dyes, and fragrances that are added to dish soap. These additives can actually have a negative effect on your plants by breaking down the cellular structure and having adverse reactions to sunlight, so it’s best to dilute the soap before use.

Because of this, if you do use this method, we recommend using a fragrance-free, dye-free dish soap such as Biokleen.

Use Neem Oil To Control Leaf Beetles

Neem oil can be very effective at getting rid of both Lily Leaf Beetle larvae and adult insects!

Not only does it eliminate the larvae, but Neem oil also repels adult beetles, preventing them from laying more eggs throughout the summer. 

Neem oil is most effective when applied within one week of the leaf beetle eggs hatching.

Neem oil will wash off with regular watering or rain and will even lose effectiveness as the oil breaks down over time. Because it will break down, you should continue to apply Natria Neem Oil at least every ten days, or as larvae continue to appear.

A bonus benefit of using Neem oil in the garden is that it is not just an insecticide, but it is also an effective fungicide and protects your plants from other diseases as well.

Diversify Plant Species To Encourage Predator Insects

The best thing you can do for all-around garden health and to encourage natural predators for pest insects is to diversify the plant species in your garden. 

Diversity is the key to a healthy ecosystem, and by maintaining many different types and species of plants, you are encouraging a wide variety of beneficial insects to populate your garden.

Add Ground Cover

While planning your garden, including a wide variety of ground cover, flowering plants, shrubs, and trees, which will all attract different types of insects and other pollinators such as birds.

By encouraging diversity in the garden, you are increasing the likelihood of beneficial predators like ladybugs and spiders as well as increasing competition.

When you have plant diversity, your garden is also less likely to fall victim to total plant loss which can occur with a bad infestation of invasive insect-like leaf beetles, or other diseases and fungi that typically affect one specific plant type.

Prevent The Larvae From Pupating In The Soil

An important part of the leaf beetle’s life cycle is the pupa phase, during which the larvae climb down or drop off of the leaf into the soil, where they build a cocoon and emerge a week later as an adult.

A great way to prevent these larvae from reaching adulthood and breeding a new generation of leaf beetles is to stop them from reaching the soil at all by using a trap like Tanglefoot Pest Barrier. This product works a lot like flypaper, with a sticky surface that traps the larvae and prevents them from making it into the soil to pupate. 

Spread a thin layer of the sticky trap at the base of the plant or on the ground immediately under the plant.

When the larvae attempt to drop or crawl down into the soil, they will get stuck, preventing them from ever reaching adulthood and reproducing! 

How To Repel Leaf Beetles Long-Term

While getting rid of leaf beetle eggs and larvae is definitely an important step to mitigate and reduce their populations, you should also make an effort to repel the adult beetles to prevent them from reproducing in the first place.

Keep reading to learn some easy tips for repelling adult leaf beetles and reducing the number of larvae you are dealing with throughout the growing season. 

Soap And Neem Oil Work Well On Adult Leaf Beetles Long-Term

We mentioned briefly that both soap and Neem oil will also work to repel adult beetles and it eliminates the eggs and larvae altogether.

Both of these products are oil-based, which coats the insect and begins to break down the waxy exoskeleton, making it impossible for the insects to retain water and stay hydrated. 

Additionally, these oils make the foliage slick and hard to move around on, as well as making them unpalatable to the hungry beetles, whose main objective is to feed on the leaves of lilies and other plants.

Keep applying these products throughout the spring and summer, about every ten days to repel the beetles and encourage them to move on and reproduce elsewhere.

Strong Herbs Can Repel Beetles

Companion planting is a method that branches off of the idea of diversifying the types of plants in your garden, but uses specific plants to serve a purpose.

Strong-smelling, acidic herbs, and plants can actually work to repel insects like beetles. 

We recommend you plant things like garlic and onions alongside your lilies and other target plants of the leaf beetles. These odorous, acidic plants will help to repel unwanted insects while adding diversity to your garden.

Use Coffee Grounds

Another great acidic additive that will help to repel leaf beetles is coffee grounds. Spread coffee grounds throughout the soil around the plants to ward off unwanted pests.

The acidity and strong smell of the grounds can cover up the attractive odors of the flowers the leaf beetles are after, while also repelling the insects from the area. 

An added bonus of using coffee grounds is that it is a great soil amendment that adds much-needed nutrients back into the soil, acting as an effective natural fertilizer that helps your flowering plants thrive.

Invite Birds And Predator Insects To Your Garden

Having a variety of flowering plants in your garden will invite other pollinators to your garden, and may even attract other types of predators like birds.

You can also put up a bird feeder near your garden to invite more birds to the area. Hang a bird feeder like this MixxIdea Metal Bird Feeder from a nearby tree or pole and stock it with plenty of tasty seeds to attract birds to your garden.

Try not to feed them too well, though, and they may turn to the leaf beetles for another food source. Adult beetles will recognize the increase in predators in the area as well, opting to leave to find a safer place to breed.

Quick Recap!

Let’s review the 8 simple ways you can control leaf beetle larvae in your garden: 

• Crush eggs and larvae by hand or knock them off of the leaves into a jar of soapy water. 
  
• Spray the larvae off with a hose regularly, cutting them off from their food source.
  
• Get some live ladybugs and let them loose in your garden to eat the larvae.
  
• Use Castile soap to eliminate the larvae.
  
• Use dish soap on larger infestations.
  
• Use Neem oil to eliminate eggs and larvae and repel adult beetles at the same time.
  
• Diversify the plants in your garden to encourage beneficial insects and increase competition.
  
• Prevent the larvae from pupating in the soil by placing sticky traps around the plants.

Hopefully, we have given you plenty of ideas to begin defending your garden from the pesky and persistent leaf beetles. Dealing with pests can be frustrating, but there are many natural and non-invasive methods you can employ to get rid of leaf beetle larvae before they mature and reproduce. 

Happy leaf beetle repelling!

References: 

Casagrande, R.A., & Kenis, M. (2004) Evaluation of Lily Leaf Beetle Parasitoids for North American Introduction. Assessing Host Ranges for Parasitoids and Predators Used for Classical Biological Control: A Guide to Best Practice. USDA. 10: 121-137. 

M. Kenis, M., et. al. (N.D.) Selection and Importation of European Parasitoids for the Biological Control of the Lily Leaf Beetle in North America, and Prospects for Control in Europe. 1st International Symposium on Biological Control of Arthropods. 416-419.

Buntin, G.D., et. al. (2004) Damage Loss Assessment and Control of the Cereal Leaf Beetle (Coleoptera: Chrysomelidae) in Winter Wheat. Journal of Economic Entomology. 97.2: 374–382.

McMillian, D.M., Fearnley, S.L., Rank, N.E. and Dahlhoff, E.P. (2005), Natural temperature variation affects larval survival, development and Hsp70 expression in a leaf beetle. Functional Ecology, 19: 844-852.