White grubs can destroy large sections of your lawn before you realize it. Learn what to look for to prevent damage and eliminate white grubs for good.
White grubs are the immature, caterpillar like stage of Japanese Beetles. Grub infestations 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 under these patches.
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 start the next generation of destruction.
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 then 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 sections 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 visibly see damage to plants in your landscape. After several weeks as an adult beetle it is time for the beetle to return to your lawn to lay eggs and start the next generation of grubs.
Mid Summer Stage– During this stage the beetle is back in your lawn and has laid eggs.
Late Summer-Fall – The recently laid eggs have hatched and these little grubs are hungry! They go up 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.
Next spring they will start the cycle all over again. Your best shot at breaking this cycle is to kill the recently hatched grubs as they move in to feed on your lawns roots in late summer.
There are two methods for killing these newly hatched grubs: Preventative treatment, and curative treatment.
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 grub larvae that is recently hatched during the late summer.
Don’t worry about the spring stage where large grubs do a quick spring feeding before becoming beetles. These grubs are hard to kill and damage is minimal during this time.
Instead, 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 late summer-fall.
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 early fall.
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:
1. BioAdvanced Season Long Grub Control Plus Turf Revitalizer
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.
2. Soctts GrubEx
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 then the active ingredient in the BioAdvanced product.
Scotts Grubex takes a little longer to activate in the soil then 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 been hatched and are actively eating your lawns roots.
Once again, I recommend holding off on curative treatments during the spring feeding.
But if early fall comes around and you think you have grubs actively feeding on your lawn then a curative treatment could be necessary.
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 in early fall then 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. A common active ingredient is Dylox. BioAdvanced Grub Killer Plus is a great product that is easy to track down.
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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