If you see lots of little brown moths fluttering over your lawn in summer, they are most likely lawn grub moths.
Some varieties of lawn grubs do turn into moths. They are small, delicate moths and are usually a tan, grey or brown shade. You’re most likely to see them at dusk, fluttering down low above the grass. They’re most common in warmer weather, but their lifecycle continues all year round.
In this article we’ll look in more detail at what these moths look like and what their lifecycle is – and also consider how to stop getting them in the first place (and getting rid of them when you do).
What Do Lawn Grub Moths Look Like?
There are a few different types of lawn grubs, although most of them look the same when they’re at the larvae stage, they grow up into different critters. The type of lawn grub we’re talking about here is specifically the moth variety, although some beetle larvae look and behave the same.
The moths themselves aren’t harmful (well, unless you count their incredible ability to reproduce and create thousands of grubs). They are small and usually a tan, grey or brown shade. They’re delicate looking, not like those large moths with the big, hairy bodies. You’re most likely to spot them at dusk, fluttering down low above the grass.
Their babies are small, pale grubs on the ground, curled round like shrimp. They are surface dwelling, unlike tunnelling beetle grubs. They’re busier in warmer weather, but their cycle does continue all year round.
It’s easier to spot the signs of lawn grubs than the small grubs themselves. These are a few indicators that you may have lawn grubs:
- Lots of small, grey or brown moths flying low over your lawn
- Brown patches in the grass where the grubs have been feeding
- Increased bird activity: those grubs make tasty treats for our feathered friends
- Grass coming up in clumps because the roots have been nibbled and damaged (although this is more likely a sign of beetle lawn grub, who burrow)
The Lifecycle of a Lawn Grub (And When They Turn Into Moths)
If you’ve noticed small greyish-brown moths flitting over your lawn and plants, they could be lawn moths planning where to raise their families. They tend to favor the lushest, healthiest grass, so it’s bad news for the careful gardener.
Having chosen their new nursery, the moths lay their eggs on the lawn, which turn into grub larvae after two to five days. The surface-dwelling larvae will now spend the next three weeks or so munching on your lawn. If you spot any brown patches, these could be a sign of feasting lawn moth grubs.
Then, larger and replete thanks to your tasty grass, they become pupae, emerging as moths a couple of weeks later. These moths in turn lay their eggs, and so it goes on.
Will My Lawn Grow Back After The Lawn Grub Moths Have Gone?
Those brown patches themselves are unlikely to grow back as the grass has been eaten away. However, you can have a beautiful healthy lawn again,with a bit of help from you. You’ll need to treat those brown patches the same way as you would treat any type of bald spot on your lawn.
Using a patch repair approach, rake up the dead grass, fertilize the soil then reseed those areas that have been eaten and damaged. Make sure you keep an eye on the young grass as it grows. Treat other areas of the lawn so the grubs don’t simply wriggle over to the next lush patch of grass. We’ll look at prevention and treatment in more detail in a moment.
So yes, if you have healthy soil and eradicate the grubs, you can have fresh new grass in the damaged area.
How Do You Prevent Lawn Grubs in The First Place?
The easiest way (and as gardeners, it pains us to say this) is to not look after your lawn so well. Those lawn grub moths are like real estate brokers, going down the block to check out the best properties. They will choose the most attractive, greenest and best-watered garden they find, and then move into their perfect new residence.
So, one solution is to ease up on the lawn care, at least during the warmer months, which is the time when moths go house-hunting. Don’t water your lawn during dry weather: sure it may get a little crispy, but it will spring back again, and it won’t attract moisture-loving moth moms.
However, few of us like the idea of letting our lawns go brown and dormant over the summer, which is the time that we want to be out enjoying our yards. Instead of prevention, many gardeners go for the “break the cycle” approach, dealing rapidly with an infestation as soon as it’s spotted.
How Do You Kill Lawn Grubs & Moths?
Our approach is to break the lawn grub cycle. If you can stop those pesky larvae from settling down in the all-you-can-eat buffet that is your lawn, you’ll prevent it from becoming a permanent, repeating problem.
There are insecticides available that will kill lawn grubs; however, we always prefer not to use these in our yard because of the effects they can have on other, more welcome animal life.
A home-made and less harmful spray can be made using soapy water. Mix liquid soap with water to create a spray that will effective smother the surface-dwelling grubs. Spray it on areas where there are signs of grub activity. Wait an hour or so then check the area. You may need to repeat it.
This may not be enough for a large infestation (which with lawn grubs, is defined as more than 5 grubs per square foot). So, the rule is to go in early, and go in hard. Apply lots of soapy water, as soon as you suspect there may be lawn grubs in your yard. The cycle tends to begin in early summer, so be vigilant from them.
If you’ve been researching killing lawn grubs, you may have come across neem oil. This is a natural insecticide that’s extracted from the seeds of a South Asian tree, and is fatty like soap. It has to be used sparingly, because even though it’s used in cosmetic products as a nutritional antioxidant, it can be harmful and is banned in some countries. We’d suggest staying clear of this one.
You’ll have no doubt also come across the milky spore solution. Milky spore is a naturally occurring bacteria found in certain soils, which is available in white powder form. You can introduce it into your garden to infect feeding lawn grubs. However, it’s used to kill beetle lawn grubs, and we don’t know if it is as effective with moth lawn grubs.
Another common solution is to introduce a grub predator into your garden. Visiting birds alone won’t keep the population down, but tiny nematodes will. These miniature worms find a grub to host them, and then release bacteria that kills the host. This bacteria passes into the soil, and so it goes on.
You can buy nematodes in liquid form (yes, really) and you simply water them into your lawn. This is an excellent, natural way to keep the grubs away, without harming the grass or less invasive critters.
We recommend starting with the soapy solution approach, spraying it liberally the first time you spot a moth or see a brown patch. If caught early, an infestation shouldn’t develop. And maybe don’t aim to have the lushest lawn on the block; a slightly less verdant lawn isn’t a high price to pay for a healthier one.
We actually think those tiny brown moths fluttering above the grass in the twilight evenings of summer are quite pleasing to look at – but we do realise they’re an indicator of grub problems with your lawn.
And although the solution for getting rid of them and keeping them away is counter intuitive (e.g not keeping your lawn in quite as pristine condition as you’d like), this is perhaps a small price to pay for avoiding those brown and dead patches of grass.
To avoid harming other wildlife in your yard when you do try and eradicate your lawn grub moths – we also recommend an organic, environmentally friendly solution like the ones suggested – so you don’t end up doing more harm than good.
Homeowner and property investor Larry Jones founded Take a Yard in 2020 to bring you the very best outdoor living content, based on his years of experience managing outside spaces. Read more >