Grubs are the #1 insect problem in most northern lawns. A grub is the immature larvae of a beetle. There are several types of beetles responsible, the most common are Japanese Beetles and Oriental Beetles. These insects spend a few weeks as adults, eating your broad leaf plants, then lay eggs in your lawn where they spend 10 months munching on grass roots.
If you have a heavy infestation, they may eat so much of your lawn’s roots that it can be rolled up like a carpet, although even lesser infestations can be harmful. Without roots, your grass cannot support itself and may die.
The simplest way of checking for grubs is to cut back a sample of turf with a shovel. Count the grubs in the top 3 inches of soil and replace and water the turf. Take several 6″ X 6″ samples from different locations. Most grubs are white or cream colored with dark patches, and have 3 pairs legs. Grubs grow up to an inch long. They’ll usually be curled up like a C when you find them in the ground. An occasional grub is ok, but if you average more than 2-3 per sample, your lawn probably needs treatment.
Grub control needs to be synchronized with their life cycle. They live for a total of about one year. Starting with eggs laid in late summer, they fatten up while eating your lawn until the ground freezes. Then they move deeper to stay below the frost line, and return to your lawn in the Spring with an enormous appetite. By mid-Summer, they mature in to beetles, eat your roses and other broad leaf plants, then lay thousands of eggs that start the cycle over again.
Fall is the critical time for killing grubs. If you wait until Spring, most of the damage will have already been done and the grubs will be much harder to kill. Most experts will advise that the best Spring Treatment is to fertilize and overseed, then wait to catch the next generation in the Fall when they are more vulnerable to insecticides. Of course, many professional lawn services will disagree and tell you a horror story about how the grubs will eat up all of your lawn and turn to eating your asphalt driveway if you don’t act right away…ignore hem and save your money for Fall treatment.