White grubs can destroy large sections of your lawn before you realize it. Learn the best products and methods for preventing and treating white grubs.
White grubs are the immature, caterpillar like stage of Japanese Beetles. These grubs can quickly, and secretively, knock out giant sections of your lawn.
And if that’s not bad enough, when they become adult beetles they can destroy foliage of plants in your landscape and vegetable garden. When the beetles are done feeding they enter back into your lawn to start another generation of lawn killing, foliage destroying insects.
Sound terrible? It is. If you suspect you have a grub problem then consider making grub control a part of your lawn care program.
How Do You Know If You Have White Grubs?
These 5 tests should help diagnose the problem:
1. Do areas of your lawn easily roll up? If you start to see areas of your lawn that look like they are dying go over and see if you can roll it up, or peel it up like a piece of carpet. Grubs feed on the root system of your lawn. Since there are no roots to anchor your lawn, large sections should easily be separated from the soil.
2. Do you see irregular brown patches in sections of your lawn? After grubs start attacking your lawns roots, you will inevitably see the damage on the surface of your lawn. Since sections of your lawn no longer have roots to take in water and nutrients you will start to see brown patches where your lawn is dying. Look under these dead patches and inspect to see if there are grubs in the soil.
3. Do you see evidence of animals digging in your lawn? Skunks, raccoons, crows, and other animals love feeding on grubs. Skunks and raccoons in particular will dig aggressively in search of a good snack. If sections of your lawn look dug up, then check under these damaged areas to see if you have grubs.
4. Do you see beetles chewing on leaves in your landscape? In the summer months grubs become adult beetles and they will feed on plants in your landscape. If you notice leaves that look like something is chewing on them look carefully and you will probably see beetles. These beetles likely came from your lawn, and will go back in your lawn to lay eggs for the next generation of grubs.
5. Peel up a one foot section of lawn using a square edging shovel where you suspect there might be grub damage. Look through the soil to see if there are any grubs. If you count just a few than that is normal. If you count more than a few it means you have a grub problem. 10 or more in a one square foot section means you have a serious infestation.
Life Cycle of a White Grub
To treat grubs it is important to first understand their lifecycle. Think of grubs as having 4 distinct stages during the year.
Spring Stage- In spring the grub is hungry and goes to the root zone of your lawn to feed on its roots. This is a quick feeding that lasts a couple of weeks so lawn damage done during this time is usually not too severe. After a couple weeks this grub turns into a beetle and flies out of the ground which brings us to the next stage.
Early Summer Stage- The grub is now a beetle and spends the summer months feeding on foliage of plants and vegetables. This is where you can see damage to plants in your landscape. At this stage the mature female beetles return to your lawn every couple of days to lay eggs. After laying a batch of eggs they leave your lawn and continue to feed. This cycle repeats until all their eggs have been laid (usually around 40-60 eggs). The adult beetles eventually die off in the fall.
Mid- Late Summer Stage– During this stage the eggs begin hatching and grubs start to feed. This is the best time to apply curative grub treatments (more on this below) since the grubs are small and easier to kill.
Late Summer-Fall – The grubs are hungry at this point and they grow fast! They go to the root system of your lawn and feed on the roots for the next couple of months. They are trying to get big and fat so they can overwinter deep in your lawns soil.
There are two ways to put an end to the destruction. One is with a Preventative Grub Treatment, and the other is with a Curative Grub Treatment (read below).
Grub Prevention Treatment
Before we talk about the best preventative insecticides it’s important to point out the importance of timing.
Grub preventatives are meant to kill the emerging grub larvae during the mid-late summer.
The key to success is to get your preventative insecticide down during late spring (late May- late June) for preventing the new generation that comes in mid-late summer.
Now, you may be wondering why you would have to apply preventative insecticides so early. It seems unnatural to put a product down in late spring to treat a problem that occurs in late summer.
The reason for this early timing is because the preventative insecticides take several months to become activated. These products are only effective once they get broken down into the soil and absorbed by the grass.
If you apply these products too late in the season they won’t be able to do their job. So fight the urge to wait and get these products down 60-90 days before Japanese Beetles lay their eggs.
For grub prevention I recommend using one of these two products:
The active ingredient in this grub preventer is Imidacloprid. It’s my favorite product for grub prevention but some states have it restricted so it can be hard to find in those states. Otherwise most big box stores should have it in supply.
Scotts GrubEx is probably the most popular and easy to find. The active ingredient is Chlorantraniliprole. The active ingredient has a reputation of being more environmentally friendly than the active ingredient in the BioAdvanced product.
Scotts Grubex takes a little longer to activate in the soil than the BioAdvanced so it should be applied earlier.
Grub Curative Treatment
Unlike the preventative treatments, a curative treatment is for killing grubs that have already emerged and are actively eating (or getting ready to eat) on your lawns roots.
Once again, I recommend holding off on curative treatments during the spring feeding since grubs are so large at that point and are able to fight off the curative treatment.
But if by mid summer to early fall you think you have grubs actively feeding on your lawn then a curative treatment could be beneficial.
Maybe you forgot to put down a preventative, or maybe you applied it too late. Maybe your infestation has been so bad in the past you want to do a preventative and curative treatment.
Whatever the reason, if your lawn is showing signs of being under attack from grubs than a curative treatment will help manage your grub problems.
A curative treatment is easy to spot. It will usually say something like ‘kills grubs within 24 hours’ on the label. My favorite product as a grub curative treatment is BioAdvanced 24 hour Grub Killer Plus
The active ingredient in this product is Trichlorfon. I usually see this product in big box stores so it shouldn’t be hard to track down.
Organic Treatment for Grubs
If you want to go the organic route for grub control than my recommendation is beneficial nematodes. These are microscopic, non segmented worms that contain a bacteria that kills grubs (and other insects). You can purchase beneficial nematodes online and also get more of an education on them here: Beneficial Nematodes
Lastly, I believe in practicing an integrated pest management approach. If you have a thick, full lawn and have no history of grubs then don’t apply any preventatives or curatives. Instead, inspect your lawn frequently so you can manage problems early on and treat when necessary.
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