Natural Control of Lilly Pilly Beetles

Have you ever paused to inspect the jagged margins of your lilly pilly leaves, only to wonder what creature could be responsible?

You’re not alone. Recently, a new suspect has been identified as the culprit behind the damage – Paropsides calypso. Until recently, another beetle, Calomela pallida, was blamed for the damage.

This article will explore integrated pest management strategies to control the lilly pilly beetle effectively.

Understanding the Lilly Pilly Beetle

To control a pest, we must first understand it. Let’s delve into the lifecycle and feeding habits of the lilly pilly beetle.

Lifecycle of the Bright Green Beetle

The lifecycle of these bright green leaf eating beetles begins when adult beetles lay their eggs on the undersides of leaves. The larvae, which are pale green grubs, hatch from these eggs and immediately start feeding on the plant.

Once they’ve matured, these grubs drop to the ground and pupate in the soil. After a period of metamorphosis, they emerge as fully formed adult beetles, ready to continue the cycle up in the leaves.

Feeding Habits of the Lilly Pilly Beetle

Both adult beetles and larvae feed on lilly pilly plants, sometimes causing significant damage when numbers get high. They chew away at the edges of the leaves, leaving behind a characteristic scalloped pattern.

Genetic Control – Choosing the Right Plants

Genetic control essentially involves choosing resilient or resistant plants to deter pests. The lilly pilly beetle shows a particular preference for lilly pillies and no other plants.

In my experience, syzygiums seem to be more susceptible than waterhouseas and acmenas. Our head breeder, Todd, agrees with this observation.

However, this is just an observation and not a confirmed fact, as there’s limited scientific information available on this pest.

Cultural Control – Maintaining Plant Health

Cultural controls are practices that revolve around the growing environment. Given our recent understanding of the true lilly pilly beetle which has been damaging lilly pilly plants, much about its biology and ecology remains unknown.

However, one cultural control method that can certainly help is preventing transmission by isolating affected plants as soon as the pests are identified.

Physical Control – Manual Removal

Physical controls are methods that involve physically removing or blocking pests from the environment. One of the most direct ways to control the lilly pilly beetle is through manual removal.

To do this, regularly inspect your lilly pilly plants, focusing on the leaves’ undersides where eggs and larvae tend to be found. Adult beetles and larvae can be removed by hand and placed into a container of soapy water to dispatch them.

While this method is effective in reducing the number of beetles on smaller individual plants, it’s labour-intensive and may not be feasible for larger infestations or gardens. However, it’s a safe and chemical-free option that can be particularly useful in smaller garden settings or for isolated infestations.

Besides this, spraying a jet of water at your plants may put a dent in the population, although hard-shelled adults may not be that badly affected.

I’ve never tried this myself, but applying a sprayed mixture of diatomaceous earth and water to the leaves, and dry diatomaceous earth (DE) to the ground could be a good method for knocking a population down, due to its ability to desiccate hard-shelled insects.

The wet spray on the leaves will need to dry before it’s effective, but the spray should help apply the DE onto every leaf.

DE is a natural product made from fossilised sea creatures, which is a good source of amorphous silicon dioxide. Be careful not to inhale DE as it can harm your lungs.

Biological Control – Encouraging Natural Predators and Parasitoids

Biological controls involve using living organisms, such as predatory and parasitoid insects, or disease organisms, to control pest populations.

As we’ve only recently identified this beetle as the true cause of the damage to lilly pilly plants, information about its natural predators is still limited. However, promoting biodiversity a dense planting in your garden is a beneficial strategy for pest control in general.

Attracting birds and other beneficial critters, such as ladybirds, spiders, and lacewings, can help keep a range of pest populations under control. This can be achieved by planting a variety of flowering plants to provide food and habitat for these beneficial creatures. Placing a small dish of water or a bird bath nearby plants can also encourage beneficial insects.

Bugs for Bugs is a company that sells predatory and parasitoid beneficial insects, but they haven’t given us any clues for what eats the lilly pilly beetles, unfortunately.

Reference

Chemical Control – Using Organic and Chemical Pesticides

Chemical control involves using pesticides to kill pests. While chemical control should generally be used as a last resort, there are relatively eco-friendly options available that are effective against the lilly pilly beetle.

White oil, which can be purchased at your local nursery or made with detergent, vegetable oil and water. This will smother the pests, but won’t affect the individuals that are not directly sprayed. Neem oil performs a similar function, but also enters the plant’s system.

Bugs for Bugs recommends the usage of neem and white oil (also known as eco oil), based on anecdotal evidence.

Anecdotally, I’ve hear ant sand can be spread around the base of the plants to disrupt the beetle’s lifecycle when they pupate in the ground. In severe infestations, products like Confidor may be used.

This systemic insecticide can be applied as a spray to the leaves or in pellet form to the soil. However, you should know that non-targeted systemic pesticides like this are toxic to a wide range of beneficial insects and should be used sparingly and responsibly, if at all.

Daniel’s Wrap

The control of lilly pilly beetles is best tackled with an integrated pest management approach, combining genetic, cultural, physical, biological, and chemical methods.

By understanding the lifecycle and habits of the beetle, choosing resistant plants, manually removing pests, attracting natural predators, and using eco-friendly and other pesticides responsibly, we can protect our lilly pilly plants.

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