At least 2,300 species of scarab beetles live in Australia, including the iridescent Christmas beetle Anoplognathus, the spectacularly horned Rhinoceros beetle Dynastinae, and the beautifully pattern flower chafers Cetoniinae.

The larvae of the scarabs live underground or in decaying wood for most of their life.

Curl grubs are a great meal for hungry birds. Shutterstock

The scarab larvae are beneficial to the environment.

The soil-dwelling larvae of the scarab can help disperse seed.

The soil is healthy when species that consume decaying matter are present.

The larvae of scarabs are usually large and rich in protein and fat. They make an excellent meal for hungry birds.

Scarabs are important not only to ecosystems but also to celebrations.

The ancient Egyptians, for example, worshipped the Sun through the symbolism of the ball rolling dung beetle.

Colourful Christmas beetles traditionally mark the arrival of the Christmas season in Australia.

Unfortunately, the number of Christmas beetles has decreased in recent decades. This is likely due to habitat destruction.

What are the effects of curl grubs on my plants?

The majority of scarab larvae feed on grass roots. This can damage plants if there are a large number.

In Australia, the Argentine Lawn Scarab, as well as the African Black Beetle, can cause serious damage to lawns and pastures.

Under the right conditions, native scarab species are also pests.

When Europeans planted sugar cane, a type of grass, and converted native grasslands into pastures, native Australian scarabs found a new abundant food source. They were then classified as pests.

We know very little about the feeding habits and habitats of native scarab larvae.

Some garden species are not harmful to plants. For example, the Eupoecila Australasiae is a beautifully patterned Fiddler Beetle that feeds on decaying wood.

Under normal conditions, even species that eat roots will not be a problem.

The plants are surprisingly resistant and can tolerate losing a few of their roots due to beetle larvae. Curl grubs can help keep soil healthy, even if they damage plants. They provide aeration and mix nutrients.

How can I tell if my garden has ‘good’ beetle larvae or ‘bad’?

Unfortunately, it is difficult to identify the species of scarab larvae. It isn’t easy to distinguish between groups without magnification. There are guides to identify scarab larvae in pastures but not for those found in gardens.

The health of the plants is a good indicator since identification may not always be possible. Damaged roots can cause plants to wilt and turn yellow.

Most exotic species of scarabs cause damage to lawn turf because they prefer grassroots.

It is difficult to identify the species of scarab larvae. Shutterstock

What should I do when I find a curl grub in my garden or yard?

It can be alarming to see suspiciously plump curbs in the roots of your prized garden plants, but don’t reach for insecticides.

Chemicals used to kill curl grubs also harm scarab larvae regardless of their pest status.

Curl grub treatments often contain “anthranilic amides,” which can be toxic for butterflies, moths, and aquatic invertebrates.

Insecticides can cause more harm than benefit by destroying native beetle larvae and disrupting soil ecosystems.

Read more: Why have pantry moths overrun my home, and how do I get rid of them? An expert explains.

So what to do instead?

The larvae that are found in wood decay or mulch will feed on the wood and compost it. They won’t harm your plants, so you should leave them where they are.

The larvae in the compost bins help to break down waste. They should be left alone.

Use your plants’ health to guide you if you find larvae on your soil. Consider leaving the curl grubs in place if your plants are otherwise healthy. Scarab larvae form part of the soil ecosystem and will not cause damage if there aren’t many.

Consider feeding them to birds or squashing them if your plants are yellow or wilted. It may not be pleasant, but it is better than using insecticides.

The larvae of nonnative scarabs are especially dangerous to lawns. Replace lawns with native grasses. This will increase biodiversity and reduce the risk of damage by nonnative larvae.