Growth Stages Of Grubs
Eliminate Grub Problems For Good
Yardeners e-mail me pleading for me to help them “get rid of their grubs”! My answer is seldom satisfying since it is “there is no way to completely get rid of grubs”. The better question is “how can I get rid of the problems that grubs are perpetrating upon your helpless lawn”.
The common approach to grub control is to apply an insecticide each year some time in June which then, if applied properly, should kill all the grubs in the root mass of your lawn. Then, if that approach was successful, we perform that routine year after year.
Grubs are only a problem because your grass is growing on compacted soil and the root system is only 2 to 3 inches deep. To avoid stress, turfgrass needs space down 6 to 12 inches. Grubs hibernate during the winter months and then they must come up in late spring to nosh grass roots for a few weeks so they then can pupate from grub to adult Japanese beetle or June beetle.
If the roots of your grass plants are only 2 inches deep, that is where the grub has to go get his spring snack. It takes only 5 white grubs per square foot in a lawn with only two inches of roots to virtually destroy that lawn if nothing is done. If the root system is down at least 6 inches deep, you can have 15 grubs per square foot and you will see no evidence of their eating the grass roots. We don’t get rid of the grubs. We fix our compacted soil so the turf grass produces more massive roots and the grub population is spread out sufficiently so those brown patches indicating grubs, never again show up.
The grub problem is fixed in the long term if we can fix our compacted soil to allow the roots to grow more deeply. We fix the soil under turf by adding a layer of organic material over the lawn each fall and/or spring. Finely chopped leaves with a mulching mower or used coffee grounds spread at ¼ to ½ of an inch applied over three to five years will serve as the stimulus for the earthworms and soil microbes to break up that compaction. That organic amendment every year serves as food for the “soil food web”, all the creatures living in a healthy soil.
So if I had grubs last year, I will probably have grubs this year. I’m just getting started adding a layer of chopped leaves, so I will have to again use an insecticide containing Merit to deal with this year’s problem . I might have to do the same next year as the roots are growing more deeply. After three years, however, you still have grubs, but they are no longer in a situation where their activity causes any visible harm to your lawn ever again.