Witchetty Grubs in Gardens: How to Deal with Them

Are you a gardener who is struggling to get rid of witchetty grubs in your garden? These plump, creamy-white larvae of the cossid moth can be a real nuisance for gardeners as they burrow into the roots of plants and trees. In this article, we will discuss what witchetty grubs are, their impact on gardens, and effective ways to deal with them.

What are Witchetty Grubs?

Witchetty grubs are the larvae of the cossid moth, which are native to Australia. They are commonly found in the roots of acacia trees and have been a staple food for indigenous Australians for thousands of years. Witchetty grubs can grow up to 10 centimeters long and are creamy-white in color with a brown head. They have a high fat content and are considered a good source of protein.

The Impact of Witchetty Grubs on Gardens

While witchetty grubs may be a delicacy for some, they can cause significant damage to gardens. The larvae burrow into the roots of plants and trees, causing them to weaken and eventually die. This can be especially problematic for young plants that have not yet established strong root systems. Additionally, the presence of witchetty grubs can attract other pests such as ants and rodents to the garden.

How to Deal with Witchetty Grubs

If you have identified witchetty grubs in your garden, there are several effective ways to deal with them:

1. Handpicking

One way to control the population of witchetty grubs is to handpick them from the soil. This method is best used for small infestations or if you only have a few plants affected. Simply dig around the base of the plant and remove any visible grubs. Be sure to dispose of them in a sealed container or bag to prevent them from returning to the garden.

A person handpicking witchetty grubs from the soil.

2. Beneficial Nematodes

Beneficial nematodes are microscopic organisms that can be used to control a variety of garden pests, including witchetty grubs. These nematodes enter the bodies of the grubs and release bacteria that kill them. You can purchase beneficial nematodes from garden centers or online retailers and simply follow the instructions on the package to apply them to the affected area.

A container of beneficial nematodes.

3. Bacillus thuringiensis

Bacillus thuringiensis (Bt) is a natural soil bacteria that produces toxins that are lethal to many insect pests, including witchetty grubs. You can purchase Bt-based products from garden centers and apply them to the soil around affected plants. It's important to note that Bt only affects the larvae of insects and does not harm other beneficial organisms in the soil.

A container of Bacillus thuringiensis-based product.

4. Soil Solarization

Soil solarization is a technique that involves covering the soil with a clear plastic sheet and allowing the sun's heat to kill off pests and pathogens. This method is best used for large-scale infestations and can be quite effective at controlling witchetty grubs. Simply cover the affected area with a clear plastic sheet and leave it in place for at least four to six weeks during the hottest months of the year.

A garden bed covered with clear plastic sheet for soil solarization.

Witchetty grubs may be a popular food item for some, but they can wreak havoc on gardens by damaging the roots of plants and attracting other pests. If you have identified witchetty grubs in your garden, there are several effective ways to deal with them, including handpicking, using beneficial nematodes, applying Bt-based products, and using soil solarization. By taking proactive measures to control the population of witchetty grubs, you can protect the health and vitality of your garden.

beneficial nematodes, Bt, soil solarization, handpicking