# Too Late For Grub Killer?



## samjonester (May 13, 2018)

I've got a small spot in my recent reno that was beginning to die off. I dug in and found this little bugger 



Given that it is now October 3, I'm wondering if it is a good idea to put down Grub Killer (Dylox). I've never personally treated for grubs, but have heard that it's something you typically do in the Spring.

A quick google on grubs leads me to believe that I will kill all my earthworms for naught, and the grubs will be back next spring. This is when they typically burrow down for the winter, correct? Or am I overthinking this, and if there is one grub with a full belly, it's still worth spreading on the whole reno despite the time of year.


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## social port (Jun 19, 2017)

I've never been able to clarify how selective pesticides are, and I generally avoid them for that reason (I like free aeration). It may vary by AI.
I seem to recall @STL posting something recently about one pesticide that would address grubs but leave the earthworms alone. Not sure though.


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## Khy (Jul 27, 2018)

social port said:


> I've never been able to clarify how selective pesticides are, and I generally avoid them for that reason (I like free aeration). It may vary by AI.
> I seem to recall @STL posting something recently about one pesticide that would address grubs but leave the earthworms alone. Not sure though.


The majority of insecticides you're going to use to kill grubs (Dylox for example) won't harm things like earthworms too much. That said, some are toxic to them, like Imidacloprid.

It's important just to read labels and such. At the end of the day though, killing the earthworms and the grubs will be more beneficial than letting them both live. That free aeration won't do jack for you if the grubs eat all the root system out from your entire lawn.

There's a handy chart here from a study done by University of Kentucky that breaks down the toxicity to earthworms of commonly used lawn/garden chemicals.


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## samjonester (May 13, 2018)

I completely agree @Khy! I would gladly kill both to stop a grub infestation.

My real concern is that the grub killer won't really be effective, or will only be effective to a small percentage of the population because of the time of year. I don't want to kill the friendlies in the ground for nothing.

That chart is very handy. Looks like it has a moderate toxicity to earthworms (Dylox's AI is Trichlorfon).


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## pennstater2005 (Jul 17, 2017)

How many grubs did you find? A healthy lawn can have so many grubs per square foot before they become an issue. I have them but haven't treated because there are only a few per square foot.


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## Hoosier (Jun 12, 2018)

I realized I had some pretty significant grub damage when I did my overseeding a week and a half ago. I went ahead and did an app of Scott's Grub Ex, which is chlorantraniliprole. Didn't have time to research before I put it down, as I only had about 24-48 hours to complete the whole seeding/repair project before a week of rain, but I can say it worked very well (would have to research if it kills earthworms)... no additional signs of turf damage, which I would expect to keep seeing if I didn't kill them. No issues with seed germination either.

Package recommends applying in the Spring, and says it will last 4 months. I also believe it says to only apply once per year, but I had a big problem and didn't want to risk more damage after putting in weeks of work seeding and watering to fix the torn up areas. I'll certainly do another grub treatment in the spring, but will probably just try to use a different chemical.

If you've never had a big grub problem in the past, you might look into Milky Spore. Basically apply a ton of scoops in a grid pattern over the entire lawn. Over a couple years, the product spreads throughout the entire lawn, and it stays active for 10 years or so. The thing is, you can't use a grub killer with this, as you actually need the grubs to stay alive and ingest this in order to infect the other grubs that eat them. I did this at my last house, and was only in the house for a couple years after applying, but never had grub problems after that, so can attest to it working. But, it does take quite a while to apply (I used the powder instead of the granular, which apparently has to be applied multiple times), and wouldn't be immediately beneficial if you have a problem already, unless you get the powder exactly where the grubs are, which I guess is possible.


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## STL (Jul 14, 2018)

samjonester said:


> I completely agree Khy! I would gladly kill both to stop a grub infestation.
> 
> My real concern is that the grub killer won't really be effective, or will only be effective to a small percentage of the population because of the time of year. I don't want to kill the friendlies in the ground for nothing.
> 
> That chart is very handy. Looks like it has a moderate toxicity to earthworms (Dylox's AI is Trichlorfon).


See the curative section here http://msue.anr.msu.edu/news/how_to_choose_and_when_to_apply_grub_control_products_for_your_lawn

Specifically:



> There are two chemicals, carbaryl and trichlorfon, that are considered curative treatments. They are short-lived compounds that kill all life stages of grubs. These two insecticides are the only options if high numbers of grubs are found in the fall and in spring before early May. Our research indicates they will kill 20-80 percent of grubs when applied in September or 20-55 percent when applied in late October.


While you're not, but since it was mentioned, there's really no need to use products that more harmful to non-targeted species when dylox (trichlorfon) and other less harmful products for spring preventative application are widely available.


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## samjonester (May 13, 2018)

@pennstater2005 thanks for the rational advice! I dug around again. The area was maybe 4 sq ft, and I only found 2 grubs. I think you're right, and based on some reading this has prompted me to do, it's not enough grubs to warrant an overreaction. This is my first time seeing a live grub, and I got freaked-out over the new lawn. I've plugged it with potted grass, and seeded around the area a bit. This was a nice opportunity to reseed another small weak spot on the edge of the lawn, too.

My plan will be to monitor for more damage. This seems to be easier to spot in younger grass, but very hard to diagnose properly. Is it damping off, pythium, some other fungus? A dry spot? Grubs? A rogue tree root just below the soil I didn't know about? It's so much more susceptible, and I'm so much more in tune with micro changes. It sometimes feels like my first born got her first cold again :lol:

Here's a bit more detail about what I'm going to do if someone else stumbles into this situation like I just did.

*Now:* If I see more damage pop up, and I see more than a few grubs per sq ft, I'll apply a *curative* grub killer like Dylox (trichlorfon). Turns out early fall is the best time for curative measures because they've recently hatched and are feeding aggressively. I'd say based on my local weather since August, I'm soundly in _mid-fall_.

*Spring:* Turns out this is an ineffective time to treat. They are coming back up to the surface for a small meal before pupating. By the time you'd see any damage, they've stopped feeding and have a protective cocoon around them.

*Summer:* This is the best time with *preventative* applications. These will remain in the soil and kill grubs as they hatch. Some mostly otherwise uninformative gardening clickbait had a catchy phrase "apply when the beetle fly" to remember to apply to areas where they're typically a problem.

A few interesting articles:

https://njaes.rutgers.edu/FS1009/
https://ento.psu.edu/extension/factsheets/white-grubs-lawns
http://msue.anr.msu.edu/news/how_to_choose_and_when_to_apply_grub_control_products_for_your_lawn


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## g-man (Jun 15, 2017)

The last article you linked is my go to recommendation. I recommend using the chlorantraniliprole since it is the least toxic to humans/bees and works really good. It does take more time to work into the soil, so it needs to be applied earlier (April/may).


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## ken-n-nancy (Jul 25, 2017)

samjonester said:


> *Summer:* This is the best time with *preventative* applications. These will remain in the soil and kill grubs as they hatch.


Early summer (well, June) is the right time to apply imidacloprid as a preventative. However, imidacloprid (aka Merit) is falling out of favor due to being believed to be damaging to honeybees and earthworm populations.

*I would instead recommend using chlorantranilipole*, which is the active ingredient (AI) in Scotts GrubEx2. It is also a preventative and has a long residual. It is much friendlier to honeybees and earthworms than imidacloprid. However, *chlorantraniliprole really needs to be applied in the spring* (I suggest early May) in order to be in the soil where it needs to be in July to kill the newly-hatched grubs at that time. One down side compared to imidacloprid is that chlorantraniliprole is also more expensive. I usually try to buy mine at this time of year when it goes on end-of-year sale. I've been watching my local Home Depot and Lowes for that to happen via brickseek.com, but I'm still waiting...

Like @g-man, the Michigan State University article you mention is my go-to recommendation for grubs. The article gets updated every year to remain current. A problem with the two older articles that you referenced (from May 2010 and 2006, respectively) is that they are from nearly a decade ago when imidacloprid was the go-to grub preventative before the damage to honeybees and earthworms was widely confirmed and before chlorantraniliprole was widely available to consumers. Given more recent findings, I'd highly suggest chlorantraniliprole with an earlier application date of early May.

http://msue.anr.msu.edu/news/how_to_choose_and_when_to_apply_grub_control_products_for_your_lawn


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## Green (Dec 24, 2017)

Ok, here's my take. (Doesn't hurt to add one more, right?)

Chlorantraniliprole (trade names: "GrubEx1" or "Acelepryn") at bag rate (2.87 lb/M for the 0.08%, or 3.5 lb/M for the 0.0675%) in April or May for prevention. Do it for at least 2-3 years in a row. After 3+ years, it might not be needed every year. Also, it's possible that resistance could develop to this group/AI of pesticide. There aren't any documented cases yet last time I checked into it, but the potential is there, chemically/biologically, so it's probably only a matter of time until we start to hear about it. The solution to resistance is rotation with a different class of AI. Problem is, there is no good alternative at this time with which to rotate Chlorantraniliprole...yet. As others mentioned, Imidacloprid is falling out of favor. It's actually now "restricted use only" here where I am (My state is very aggressive with pesticide regulation.). Lawn companies, such as TrueGreen, still use it because it's inexpensive, effective, proven, and low toxicity if used right. But it's being phased out more as time goes on. It definitely leaves something to be desired with the collateral damage.

A possibility might be to rotate with a natural product. Which brings me to...

Milky Spore, as someone mentioned. I looked into it. Decided against it, because research studies showed that it does not overwinter in the Northeast/mid Atlantic, or other areas that get cold.

That leaves only one other product. "GrubGone". It's so new that it's not even registered in most states yet, but it's organic, and studies show it's effective. It should be on everyone's radar. I've posted a bit about it in the past.

Finally I have no advice for grub killers/curatives, as I've never had to use one.


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