How to Apply Lime to Lawn to Kill Grubs
For some, a lush green lawn is a crowning achievement. If you have a grub problem, these pesky insects can ruin a beautiful lawn by laying eggs and feeding on the roots of the grass, resulting in bare spots that will leave your lawn less than attractive. There are a few ways to rid your lawn of these pests, the most common being a lime application.
Determine the extent of the infestation. Most grass can handle 10 grubs per square foot. With a flat spade, cut back a 6-inch by 6-inch sample of your lawn. Count the grubs in the top 3 inches of soil. Continue this procedure around your lawn approximately a dozen times to determine your problem spots. You should apply lime to areas containing more than three grubs.
Check the ph level of your lawn before applying lime. Ideal ph should be 6.3 to 7.0. Spoon a small amount of soil from various areas around the yard. Put the soil samples in separate marked sandwich bags (i.e., near tree, near garage), then shake. Test the soil samples with a ph test kit (can be found at your local gardening or home improvement store). Note that lime will make the ph of the grass more alkaline. Using too much could affect the growth of your grass.
Purchase pelletized lime from your local home improvement store. Pelletized lime is finely ground agricultural lime mixed with a cementing agent to make pellets. It is more expensive than ground lime, but when applied, does not create dust. The lime pellets will dissolve during the first rain.
Apply the lime in early fall. Dump the pelletized lime into a drop spreader or spinner spreader. Evenly distribute pellets over your problem areas.
In the spring, the grubs have already done most of their feeding. At this point, adding more seed is a better alternative to cover bare spots. Grubs most often return to the same area, so in the fall, test the spots previously tested.
Check the ph level of your lawn after applying lime, using the same process as in Step 2.
Check the effectiveness of the lime by testing for grubs on an annual basis. The Rhode Island Landscape Horticulture Program suggests planting shade trees to deter grubs from coming back as well.