Are Grubs Good For The Garden? Here’s The Truth!


Garden grub

Have you seen evidence of grubs in your garden or lawn and you are wondering if they have any beneficial purpose? Many people wonder if they should just leave the grubs to do their thing as they are unsure if the grubs have a beneficial role to play in the ecology of your garden, like earthworms. But, are grubs good for your garden?

Grubs are most definitely not good for your garden. Grubs are pests that feed on the roots of all types of vegetation from plants to grass. They can cause irreparable damage to plant and vegetable gardens and destroy lawns. You must kill the existing grubs and then take the necessary action to protect your garden from further infestations.

Are grubs good or bad for the garden?

Grubs are very bad for your garden!

It doesn’t matter whether you have a pristine lawn with beautiful grass, a garden with flower beds and blooming plants, or you cultivate vegetables, grubs and the insects they grow into will eat and destroy all forms of vegetation if left to their own devices.

Grubs eat the roots of vegetation under the soil, when they are in the larvae stage, but they will also eat the vegetation above ground as they mature and break through the soil when they grow into adult insects.

What are grubs?

Grubs are the larvae of plant-eating insects – almost always beetles.

Beetles burrow into the ground and lay their eggs in the soil near vegetation. They are garden pests that can devastate plants, grass and vegetables and destroy years of hard work in the garden if not dealt with quickly.

Most garden and lawn grubs will be small white worm types pests that can vary in size depending on their stage of development.

The most common type of grub in the US is the larvae of the Japanese beetle. These beetles can devastate your entire garden and lawn by eating every type of organic material that is in their path both as larvae and as adult insects.

Where did these harmful pests come from?

The Japanese beetle was introduced to the US completely by accident as the beetles were transported to the States as unseen grubs on potted Japanese iris roots. Before this these beetles were only found in Japan where the population was controlled by natural predators. Additionally in Japan the beetle was prevented from migrating to different land masses due to the fact that Japan is surrounded by water.

When the beetle was introduced to America it was able to reproduce quickly and spread fast over land.

Even though in 1912 a law was introduced prohibiting the import into the USA of plants that were rooted in soil, a slack approach to implementation of the law meant that by 1916 the Japanese beetle had made America its new home and hence a new garden pest was born.

Do grubs harm plants?

All types of plants are at risk from grubs.

In the larvae stage of the beetle, grubs will feed on the roots of any vegetation that is close by. Grubs do not differentiate between plants. They are not picky eaters and will devour any type of organic material in their path.

But, unfortunately, the attack on your garden isn’t limited to the roots of vegetation below the soil.

Once the grubs mature into adult insects these insects then proceed to feed on the leaves and stems of your plants. This two-pronged attack, against foliage and roots, usually leaves plants with stunted growths and poor foliage growth. If left untreated theses attacks will often lead to the death of the plant.

Do grubs harm vegetables?

Vegetables are obviously just at risk from grubs in the soil as other plant types.

As the grubs attack the roots of the vegetables they will cause irreparable damage to plant affecting its growth and its production of vegetables. This root damage means that insufficient nutrients get to the plant and foliage, in turn leading to poor crops.

As the grubs mature and turn into adult insects these beetles then start to feed on the foliage and vegetables growing above ground causing further damage to your crop.

Any vegetables growing below ground are eaten along with the roots of the plant.

Do grubs damage lawns?

Grubs cause just as much damage to lawns as they do to gardens that are used to cultivate vegetables or flowering plants.

Lawn grubs will completely destroy your lawn if left untreated. These grubs will eat any type of organic matter and that includes the roots of your grass!

Grubs will leave a path of destruction on a lawn that is seen as damaged or bare patches. You will likely see large areas of the lawn grass turning brown. If you do not treat lawn grubs they will eventually eat their way through the entire lawn.

If the devastation the grubs cause, by their eating habits, isn’t enough you will also have to deal with other garden intruders. Grubs attract other unwanted guests into your garden.

Grubs are tasty snacks for many unwelcome garden guests that include, but are not limited to, rodents, skunks and raccoons. These creatures will become a major nuisance and create their own carnage on top of the damage the grubs are doing, as they will dig up your lawn and garden to get to the grubs under the soil.

How to deal with a grub infestation

Let’s a take a look at some effective ways for dealing with a grub infestation in your garden or lawn.

I will also give you some important information for protecting your lawn from future attacks also.

Even if there are currently no sign of grubs in your garden or lawn you should still take preventative steps as Japanese beetles are a major, and prolific, problem in the US. The small amount of effort it requires to protect your garden from these pests well outweighs the struggles you will have should grubs get into your garden at a later stage.

How to kill grubs in the garden

There are two approaches to killing grubs in your garden:

  1. The natural approach.
  2. Using insecticides.

When it comes to flower gardens I prefer to use a natural approach first. Only if that does not produce the type of results that I expect to see will I turn to an insecticide. Natural treatments are not only better for your garden and plants but they are better for the environment as a whole. Natural treatments are not only less harmful to the environment and your vegetation in themselves but even their manufacturing processes are greener and more Eco-friendly.

When it comes to vegetable gardens I will always use a natural solution for dealing with both pests and disease, and I only ever resort to a chemical insecticide if it looks very likely that I am about to lose a plant after multiple attempts to treat it naturally (very rarely happens thankfully and only usually because the problem has been left unattended for too long for by a novice gardener).

How to get rid of grubs naturally

Luckily there is a completely natural way to get rid of grubs in your garden. This is my preferred method for dealing with a grub problem in both flower gardens and vegetable gardens. It is very effective. It involves the introduction of a beneficial healthy bacteria to the soil.

There are two ways to do this.

Milky Spore Powder

One way to do this is via milky spore powder. This powder, containing specific bacteria, is introduced to the soil to kill Japanese beetle grubs.

St Gabriel Organics have an excellent milky spore power that is designed to kill Japanese beetles and their larvae, (the biggest cause of garden grubs in the US), that will work on any grub infestation in your garden.

This approach is really rather ingenious. The grub is eats the milky spore. The bacteria contained within the powder then multiples inside the grub killing it. As the grub decomposes the milky spore is released back into the soil where it stays dormant until eaten by another grub. The milky spore can remain in the soil for up to 10 years killing many different generations of grub and stopping infestations from recurring.

As this approach is a completely organic process this solution is not just Eco-friendly but it is also harmless to children, pets and wildlife, such as birds, and is completely harmless to beneficial insects such as bees.

The only problem with milky spore powder is that it’s designed to target Japanese beetles only. If you have multiple grub species in your garden you will need a solution that targets different types of grubs.

Nematodes (the preferred solution)

The better organic option for tackling all kinds of garden and lawn grubs are Nematodes.

Nematodes are a great solution for dealing with lawn and garden grubs as they will attack and kill many different types of grubs from Japanese beetles and weevils to billbugs to sod webworms and everything in-between.

Nematodes are are a specific type of bacteria that grow into microscopic worms. Like the bacteria in milky spore powder these worms attack the grub from the inside, killing it quickly.

BioLogic’s Scan Mask is a great product for dealing with all types of grubs as well as fleas and fungus gnats. I use this product.

An alternative to BioLogic is Grub-Away® which targets many different grub species. Although Grub-Away is very effective at eliminating grubs it doesn’t do much else (though to someone with a grub problem this may be more than enough!). I personally prefer the BioLogic product simply because it does not just target grubs but kills 230 different types of pests meaning this one solution covers a lot of bases and the nematodes are also grown in the USA.

The frustrating thing about the BioLogic product is that sometimes it can be difficult to locate, even online. As a back-up I will use Nema-globe which is an equally excellent product at targeting all types of grubs and fleas. Unfortunately, it doesn’t eliminate anything else though. So, obviously with 230 different pests being targeted by the BioLogic product it is a better choice but if you can’t get it use Nema-globe instead.

How to kill grubs in your lawn

Although I prefer using an organic solution for treating pests on most vegetation, especially in vegetable gardens where you will be eating the “fruits” of your labor, you can use a store-bought insecticide solution to deal with the grub problem on your lawn. Just be sure it is safe for pets and children.

Bonide’s Grub Beater is a very effective treatment for eliminating grubs from lawns. A 6 lb bag will cover approximately 5,000 square feet. The manufacturer states that it only needs to be applied once per year but to make sure you totally eliminate the grub problem and prevent future recurrences I would apply it more often.

The problem with most chemical grub treatments is that they do not penetrate deep enough into the soil. As grubs mature they make their way closer to the surface before eventually breaking through and attacking vegetation above ground as fully grown insects. Most insecticide treatments will simply kill the mature bugs that are close to the surface of the soil without seeping deep enough into the soil to reach and kill the newly laid larvae.

I find that Grub Beater is the best chemical insecticide at reaching deeper levels of the soil where it can kill the newer larvae (though I still prefer an organic approach). I’m sure there are equally good products out there that I don’t know about but from the ones I have tried Grub Beater works best.

If you find that your grub problem keeps recurring even after several treatments consider aerating your lawn before applying the next treatment. The soil may be too compacted for the product to reach lower soil levels and aerating the soil effectively should break it up enough to help the treatment reach those lower levels.

How to keep grubs out of the garden

There is an old saying that it is apt in most situations but never more so than it is in garden care. The saying goes, “prevention is better than cure“.

Taking steps to prevent grubs from taking hold in your garden or lawn in the first instance is the best way to ensure you never have to deal with these pests nor experience the damage they can do.

The milky spore approach I covered above is a great organic way for preventing Japanese beetle grub infestations in your garden or lawn. As the milky spore continues to be active for up to 10 years just one application is all it takes to treat a current Japanese beetle grub problem and prevent futures recurrences for many years to come. However, although it gives exceptional protection for many years against Japanese beetles and their larva it doesn’t target anything else.

By far the best way to protect your lawn and garden from many different types of grubs is to use a product with specially selected nematodes. BioLogic make a great nematodes product that can target up to 230 garden and lawn pests including multiple grub species. This is my “go-to” product for dealing with grubs in the soil and for preventing their re-occurrence.

Unfortunately, sometimes BioLogic nematodes van be difficult to get hold off and on those occasions I use Nema-globe which is just as effective but only targets beetle grubs and fleas.

The birds

If you have ever seen Alfred Hitchcock’s The Birds, then you know how devastating a bird attack can be. Luckily though, birds don’t attack humans but they do love tasty grubs!

Consider attracting birds to areas in your garden where they can nest. By setting up a few bird houses filled with feed you will attract birds to them. After a while when birds start using the houses  you can stop putting food in them, or reduce the quantity significantly. Some birds will start to nest in the houses.

If your garden has, or ever develops, a grub problem the birds nesting nearby will feed on them and this can greatly reduce grub numbers and in some instances eliminate the problem completely.

Although this is probably not going to be a complete solution for you it will help to remove many grubs from the soil in your garden. If you use this approach in conjunction with a good nematodes product you can be assured that the birds will remain unharmed and you will have a grub-free garden and lawn for years to come.

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