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Grubs 101

June 1, 2013

You can see crabgrass and you can see dandelions.  But one of the most damaging lawn problems you can’t see at all – not until it’s too late.  I’m talking about grubs, which will eat the roots right out from under your lawn.

The visual warning of brown grass patches in late summer and fall and next spring can be too late. Infested lawn areas often turn yellow and then brown after the damage is already done. In severe infestations, your sod can often be peeled back like a carpet. Unfortunately, the entire lawn may then have to be replaced.

Here is how the grub cycle works:

In early spring mature grubs awaken from hibernation and begin to work their way up from deep in the soil to just below the grass surface.

In late spring, these grubs change into a pupae stage before turning into beetles that later feed on roses and other shrubs and trees in your landscape.  Here are links to show you some of the more common beetles (adult grubs) that you may see this time of year hanging around your roses, garden or porch light at night:  Japanese Beetle, May and June Beetles, European Chafer, Northern Masked Chafer, Green June Beetle, Aphodius Beetle, and Oriental Beetle.

In summer, these beetles burrow into the lawn and lay eggs that will hatch into grubs.

In late summer and early fall, newly hatched grubs feed heavily on your grass roots before hibernating for winter. It is during this time that young grubs do the most lawn damage as they gorge themselves prior to hibernation.

The good news is that you can kill grubs before they destroy your lawn. You can easily protect your lawn investment with a single application of Scotts GrubEx, which provides season-long protection.

The ideal application timing is May or June prior to the time when adult beetles lay eggs in your lawn. The GrubEx protection kills newly hatched grubs before they get large enough to damage your lawn.

GrubEx doesn’t harm earthworms, which are so beneficial to your soil. Even though you rid your lawn of grubs, you may still get the occasional mole in your lawn feasting on any earthworms living in your soil.

One last tip… Be sure to water your lawn after spreading GrubEx.  Click here for more GrubEx info.

And by the way, you can kill Japanese Beetles and other plant eating insects before they destroy your roses and other plants.  Click here to get more info about Ortho Flower Fruit Vegetable Insect Killer.

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  1. Roger Rowles permalink


    Central Iowa. Is now the best time to apply GrubEx?

  2. Jack permalink

    Is it a good time to apply in Southern Massachusetts?

  3. Jack permalink

    Thanks Ashton!!

  4. Roger Rowles permalink

    When applying GrubEx, should the lawn be dry, should there be dew on the lawn, or does it matter.


  5. Roger Rowles permalink

    On another subject. When mowing is it better to mulch or just use the side discharge?



    PS – To help with a discussion with the wife.

    • Hi Roger Mulching is better as you are returning some nutrients back to your lawn. If you are mowing frequently, side discharge will be similar to mulching because the clippings will be very small so they will break down readily in your lawn. (Not sure if I helped your wife’s or your side of this discussion.)

  6. Brian V permalink

    Hi Asthon,

    How long after I drop the GrubEx can I apply a fertilizer like Weed & Feed? The same goes with the Scotts Insect Killer?


  7. Jared permalink


    Couple questions….

    -If I apply a granular weed and feed fertilizer, do I have to wait a little while after before applying some new seed to thicken some areas and overseed?

    -I did put some grubex down but I also notice in my lawn I have some ants and tiny insects running around. Can these harm my grass and should I be treating them with something else?


    • Hi Jared! Putting down a weed & feed will mean you will need to wait a month before seeding. This would suggest you will seed these areas in late summer/early fall OR, seed them now and hold off putting down a weed control until the new grass has been mowed 4 times. I would suggest the weed and feed now and then seeding in fall. Apply your weed & feed to a moist lawn on a day when rain is not expected for 24 hours. GrubEx takes care of many kinds of grubs and a few of the lawn damaging insects, however not ants, fleas, ticks, chiggers, etc. You can apply Ortho Bug B Gon MAX granules to provide broad control of a wide range of insects (however, not grubs… so you GrubEx application is not in vain). Water after application.

  8. Jared permalink

    Thanks Ashton. In terms of the damaging insects and ants you talk about, what is the damage they cause to your lawn?

    • Hi Jared Insects like sod webworm, cutworm, armyworm and chinch bug can thin your lawn and cause it to turn brown, kind of like it would look during a drought. Sometimes sections of the lawn will be killed and need to be replaced. Some grass types are more resistant to these kinds of insects. Also, these insects are more prevalent in some areas of the country than others.

  9. Rosemary permalink

    Do I apply the whole bag of Grub Ex 5000sq. Ft. even if my square footage is not that much? I would also like to fertilize is this possible at the same time if the fertilizer also has to be watered in?

    • Hi Rosemary
      Suggest you use the GrubEx spreader setting on the package and not apply too heavy. Maybe there is a neighbor you could share the partial bag with. Or seal it up tightly and save till next year. I generally recommend allowing a week between applications, however GrubEx and Turf Builder Lawn Food could go down the same time before watering. I would spread the Lawn Food first, because when you make your second application with GrubEx you may get confused by which spreader wheel mark you are looking at: the ones created when you fed, or the one you are creating now with your GrubEx application. This way you will be less likely to miss an area or over spread an area of your lawn with your Lawn Food.

  10. Denis permalink

    Hi Ashton, is it safe to add lime, starter fertilizer, grubex (had grubs/moles in prior lawn), and insect control (I have ants coming through topsoil) all at the same time prior to laying sod (sod comes in tomorrow or Friday). Also, what insect control would you recommend?


    Ontario, Canada

    • Hi Denis
      It would be best to till the lime into your soil prior to sodding (I am assuming a soil test told you that you needed lime and how much lime you needed). Then apply Starter Lawn Food on the surface of your soil prior to sodding. GrubEx is not available in Canada (sorry). Check with your local Garden Center for an Ortho product to take care of your ants. This could be done after you sod or before.

  11. erica permalink

    what happens if you happen to put down too much grubex?

    • Hi Erica
      I assume you mean too much being applied at a single application because of a faulty spreader or wrong spreader setting. Water your lawn with at least 1/4 to 1/2 inch of water as soon as you can. You should not experience any damage to your grass. If you actually mean too much from multiple applications this year, again you will not injure your grass. You will not really gain improved control of a grub problem from multiple applications as a single application applied at the proper time and watered in generally gives adequate control.

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