Getting Rid of Grass Grubs in NZ

We are fortunate not to have too many pests to ruin our gardens and lawns, but grass grubs in NZ are certainly proving to be some of the most devastating.

Whether you want to learn how to get rid of grass grub, or you simply want to understand the grass grub lifecycle in NZ, then read on. We’ll give you the lowdown so you can act swiftly and give those ghastly grubs their marching orders. 

What are grass grubs?

Awful. That’s what grass grubs are. Awful. Out of all insects in New Zealand, they are considered one of the most significant pasture and lawn pests that we have. They start as eggs from bronze beetles, turn into larvae, then emerge as adults from their pupae. 

In grass grub form, they are little, squirmy, white insects that live around 15 centimetres below your lawn’s surface. When they are adults, they are large bronze beetles that congregate around your prized shrubs and fruit trees.

How do you know you have grass grubs?

Given that grass grubs live around 15 centimetres below the surface of your lawn, how do you know you have them? Surely if they aren’t on the top of your lawn, they aren’t a problem? A common sign that you need to start controlling grass grub pests in lawns is a patch of yellow, dying lawn.

Of course, many things cause a lawn to die, but in the absence of any other problems, grass grubs in NZ are likely to be the culprit.  

The grass grub lifecycle

Learning how to get rid of grass grub is a combination of understanding the grass grub lifecycle and acting fast. Towards the end of spring and into summer, around November and December, grass grub eggs are laid in the soil. After two weeks, they hatch and start feasting on the roots of your grass.

While they’re snacking on your luscious lawn, they’re growing rapidly. When they reach their peak size, they are around 25mm and have left devastation in their wake. At this point, you may notice that you’ve got an irregular, patchy lawn that’s beginning to turn yellow and die.

Anywhere from October to December, grass grubs turn into their adult form, bronze beetles. You might think that beetles are less of a problem, but they just cause another set of issues with which you’ve got to contend.

Once they are adults, they gather in huge numbers and feast on your shrubs and fruit trees. As if it weren’t bad enough that you were killing your lawn! Now, it’s time to act and figure out how to get rid of grass grub once and for all. 

How to get rid of grass grubs

The moment we’ve all been waiting for – how to get rid of grass grub. What people find quite tricky about dealing with this ghastly grub is that they work away behind the scenes. You don’t know they’re destroying your lawn until they’ve done it.

Fortunately, there’s a way to both discover the grubs and send them packing. Firstly, you can often notice that grubs might be an issue when your lawn is suddenly the bird population’s favourite in your neighbourhood.

Heavy grub infestations are a banquet for the birds, which can lead you to need to fix the damage of both the grubs and the birds.

To confirm that you do, in fact, have grass grubs, grab a spade and dig a neat square out of your lawn about the same width as the spade. Tip the lawn square upside down and look for grubs. If you notice two or more, then it’s time to look for grass grub killers.

There are many grass grub killer products for sale in New Zealand, so we’re quite fortunate in that regard. Still, finding the right one is not all that easy. You can visit your local garden store, and ask for recommendations. There are plenty of safe options out there that you can apply before you even have a grass grub problem.

You can also purchase a dedicated spray for shrubs, trees, and foliage affected by bronze beetles. So, talk to your local lawn care provider or garden store expert about what you might need to tackle the problem.

When to treat grass for grubs

You can take action on grass grubs in NZ while they are a problem or before they are a problem. Many grass grub killers are recommended for application from February to late autumn, but also from spring to summer. 

Make sure you water the granules into the soil, and it’s even better if you are expecting moderate or heavy rainfall. If rainfall isn’t on the horizon, then deep watering is a requirement so that they can take full effect.

The best time to notice grass grubs in NZ, so that you know when to treat for grubs, is from December to March.

Goodbye to grubs

If your lawn is your pride and joy, then staying on top of any potential grass grub problem is necessary. While a lawn care service provider can assist, there’s also no harm in being aware of the signs that these little critters could be a problem. Check your lawn, buy grass grub killers, and jump into action.