Summary: Controlling lawn grub worms begins by recognizing the symptoms which can be seen when patches of brown grass in ever-widening areas continue to expand, compliments of the Japanese beetle. Homeowners mainly use insecticide for treatment and control of grub worms. Read on…
Question: Our lawn is showing patches of brown that appear to be growing. If you grab the grass it can be lifted up. What could be causing this? Vanessa, Somerset, KY
Answer: Vanessa, it sounds like what are describing is damage from a grub infestation. You need to look into controlling the culprit – the Japanese beetle lawn grub worm.
If you are seeing patches of grass turning brown and the area is ever-widening, Japanese beetle grubs may be at work.
When injury is severe, the grass can be lifted readily (just like the symptoms you described) and almost rolled back like a carpet – and the grub worms may be seen underneath at the outer rim of the brown patches, where the grass is still green.
These grubs feed on grass roots cutting them 1 to 2 inches below the soil surface. This type of injury is most likely to occur in August and September and in mid to late spring. Newly damaged grass wilts quickly on hot days. In some cases, a prompt thorough watering will enable the turf to reroot and so survive.
Lawn Grub Control & Treatment
Once you detect Japanese beetle grubs, your method of attack is to use an insecticide. Years ago an application of six pounds of 10 per cent DDT or five pounds of 5 per cent chlordane dust per 1,000 square feet would check the grubs as soon as water moved the insecticide into the feeding zone… but those days are long gone.
Now there are several pesticides on the market to kill grubs in lawn and grass. Diazinon has been around for years and is an old standby for the home gardener. Diazinon is effective, but the downside is the insecticide can take 3 weeks to put a killing on the grubs in the treated area.
When to Treat for Grubs?
Grubex from Scott’s is effective and long lasting pest control but like diazinon can take 3 weeks to kills the grubs under many conditions. Scott’s recommends applying Spring to Late Summer before insects hatch to prevent turf damage.
But it is probably better to apply around July once you know numbers of adult grubs are high, soil moisture is low to keep egg laying concentrated.
What Is A Grub Worm?
Grub worms are the larva of various insects with the vast majority of them coming from the beetles, which in itself is not a surprise considering the fact that most insects belong to this group.
Japanese beetle larvae are especially notorious when it comes to destroying lawns and they also represent the biggest grub beetle threat in North America.
Lawn grubs are at their worst around August when they start to surface, destroying pretty much anything (but mostly roots) they can get to grow up and finish their metamorphosis.
The fact that they are destroying anything they can find in the ground is bad as it is, but they bring another negative aspect with them. That is the other predatory animals that like to feast of them.
This can be a very bad combination for your lawn and the grubs living in the garden.
It’s a cliché, but the best counterattack is prevention!
I realize it often feels annoying to hear this, but the best solution is to prevent these little root eating worms from being able to damage your grass in the first place.
If they are not there, they naturally cannot do any harm. How can you prevent them from being there, or deal with them once your lawn has a worm infestation?
The good news is that there are several working solutions for you.
How To Prevent Grubs In The Lawn?
1. Do Not Mow Your Lawn
In order for the grubs to get into the ground in the first place, a beetle has to lay its eggs. As it turns out, they don’t really like to do that in long grass.
Lawn grubs don’t really like to lay their eggs in long grass!
You can cut your grass of course, but keeping it relatively long can help you prevent the insects to look at your property as an incubator. There are other ways of keeping the little lawn destroyers away, like:
2. Over-Seeding Your Lawn
Over-seeding is much healthier than overeating, and in this case it can be extremely beneficial for the general health of your lawn. Again, grubs aren’t just a problem, they attract problem.
When they eat your plants’ roots only to end up as the food of an animal that will do equally big damage to your garden, well, that’s pretty much the worst case scenario as far as grub infestations go.
By over-seeding your lawn during the spring and early fall, the grass will simply be too dense and thick for the beetles to find it accommodating.
3. Fertilizing Your Lawn A Valuable Ally
When it comes to insect-related plant problems, fertilization can be a very valuable ally. People tend to fear this process these days, but in reality it is still the most potent weapon against certain pest.
4. Water The Lawn Is Not Always Good
Lawn grub eggs have a dirty little secret, without enough water, they cannot hatch.
While it’s true that your lawn needs to be watered frequently during the hottest months and coincidentally the grub eggs hatch around the same time (early August), you can circumvent this problem by changing your watering schedule.
See, your lawn is perfectly fine with getting a lot of water once, instead of you spanning your watering activities over several days.
If the eggs do not get frequent moisture, their chances of ever hatching will reduce significantly.
5. Applying A Beetle Grub Poison
Fertilization can help you prevent the problem while poisoning is a measure for the times when you realize that the grub eggs have already been laid down.
There are certain garden chemicals that contain potent – but to humans not really dangerous – chemicals, like imidacloprid or halofenozide.
Merit insecticide [amazon] is a product like that, and it will poison the grubs when they hatch. Make sure to educate yourself about the product though, as some can affect (or even kill) the birds that would eat the grubs.
Penn State University also suggest using neem oil – “Another alternative is neem oil, a botanical pesticide. Extracted from the tropical neem tree, neem oil contains insecticidal properties and can act as a repellent, deterring feeding, insect growth and egg laying. Mix the neem oil with water as directed on the label and spray the diluted solution generously on affected areas.”
6. Wasp attack
Despite their reputation, parasitic wasps can actually be beneficial insects for more than one reasons. Certain types (ground hornets, which really are wasps) hunt grubs and will in fact seek them out to take care of the problem for you.
Okay, they’ll be more driven by their predatory instincts than your wishes and hopes, but it’s the end result what counts, right?
7. Attract Birds To Eat Lawn Grubs
Another counterattack comes from Mother Nature herself, birds. Yes, birds can actually cause quite a ruckus themselves, but overall they are still beneficial to your garden.
You should take measures to protect your seeds from them, but they will also snack on the grubs which is ultimately something we want.
How can you attract birds to your garden? It is easy. Simply put up a bird feeder close to the problematic areas, and let them go to town on it.
This may be a more of a “solution” that is not very dependable and would be low on my list of remedies!
8. Kill Grubs In Your Lawn With Beer
Yes, it’s not just you who’s likely quite fond of beer (sorry if I’m way off), but these slimy little lawn enemies as well. This idea may sound like a waste of a fine beverage, but you don’t have to use the best stuff, they aren’t really picky about it.
Simply dig a hole big enough to accommodate a plastic container of your selection (it shouldn’t be too big or too high), and pour the stuff in it. After that, all you have to do is wait until the morning.
You may also collect a bunch of slugs and snails. This may be possible in a small area but a large lawn just not very practical.
9. Apply Milky Spore Grub Control Mix
This commercially available method called “Milky Spore Disease” [amazon] is especially potent against Japanese beetle. It mostly works as a preventive measure.
It’s an organic compound that attacks larvae of Japanese beetles. It can be applied with a spreader anytime from spring through fall. It suppose to kills grub for 15 to 20 years.
Harmless to all other living things and will not effect birds, bees, beneficial insects, fish, animals, plants, or humans. a 20 Provides up to 7,000 square feet of coverage.
From St Gabriel Organics – Milky Spore Grub Control Spreader Mix features are:
- Organic Compound That Attacks Larvae Of Japanese Beetles
- Apply With Spreader Anytime From Spring Through Fall
- Kills Grubs For 15 To 20 Years, Providing You With The Ultimate Coverage
- 20 lbs provides Up To 7,000 Square Feet Of Coverage
10. Apply Parasitic Nematodes To Your Yard
Sounds frightening, but parasitic nematodes [amazon] will mostly affect the grubs, though not all types.
- Beneficial Nematodes are an organic and most effective way to battle soil pest.
- Kills Over 200 different species of soil dwelling and wood boring insects.
- Easy to apply and Harmless to humans and pets.
- 10 million Nematodes are enough for the preventative control of soil dwelling insects in approx. 2,000 – 3,000 sq.ft of surface area.
- For best results or for high infestations. Multiple releases are recommended.
Some species of white grubs will be more susceptible to the method than others, but they work excellently against the most widespread type (Japanese beetle).
Why does this matter?
Simple, if your lawn has large brown spots and with a little tug the grass can be pulled up like a bad toupee, you have grub worm damage or the larvae of Japanese beetles. You now have some ideas on what you can do to eliminate the problem.