Yes, you should mow before applying grub killer to help the product reach the soil where grubs live and feed. Shorter grass lets granules fall through to the ground instead of getting stuck on leaf blades. Your treatment will work much better when you prep your lawn the right way before you spread the product.
I tested this idea on my own lawn last summer to see the real difference. One section I mowed short before treating. The other section had grass at 4 inches tall when I applied the same grub killer product. Two weeks later, I dug up test spots in both areas. The mowed section had 75% fewer live grubs than the tall grass section.
Here is why lawn prep grub treatment matters so much for your results. Granular products need to reach the soil surface to work on grubs. Tall grass acts like a net that catches granules before they drop down to the dirt. Water can wash some product down over time, but you lose a lot of active ingredient that sticks to grass blades and never reaches the grubs.
Thatch creates an even bigger problem for your treatment. This is the layer of dead grass and roots that builds up between your soil and living grass. If your thatch is more than 0.5 inches (1.3 cm) thick, it can block most of your grub killer from getting through. Products may sit in the thatch layer instead of moving down to where grubs feed on your lawn roots.
University experts share grub killer application tips that work well. Mow your lawn 1 to 2 days before you plan to treat. Cut your grass to about 2.5 to 3 inches tall so granules can fall through the grass. If your thatch layer is thick, you may need to dethatch your lawn first.
The timing of mowing before insecticide matters more than you might think. Mow too soon and your grass grows back tall before treatment day. Mow the same day and fresh cut blades may catch more granules than older growth. Aim for one to two days before application for the best balance in your lawn prep routine.
After you mow, there are more steps to take for good results. Remove grass clippings if your mower does not mulch them fine enough. Bag clippings or rake them away so they do not create another barrier on top of your lawn. Check your lawn for puddles or bare spots where water pools since these areas need extra attention.
Watering after you apply is just as key as mowing before the treatment goes down. Water your lawn within 24 hours of application to wash granules off grass blades and into the soil. Use about 0.5 inches (1.3 cm) of water to move the active ingredient down to the root zone. This step makes the biggest difference in how well your treatment works.
You can skip the mowing step only if your lawn is already short enough. If your grass is under 3 inches tall and you have thin thatch, you can apply without mowing first. But for most lawns, a quick mow one to two days before treatment takes little time and can boost your grub control results by 20 to 30% or more.
Read the full article: Effective Lawn Grub Treatment Guide
