Can I Treat for Grub Worms 5 Weeks After Laying Sod?

Best Time to Treat Grubs

• The best time to treat grubs with a pesticide is in mid-June, as suggested by the Maine Department of Agriculture, Food and Rural Resources. Avoid treating in the spring, because it will not effectively remove grubs. Grubs emerging in the spring are already mature and are difficult to kill with pesticides. If you laid new sod in early May, treat your grub problem five weeks later if your pest population warrants treatment. Grub problems that are not severe can be treated through cultural methods.

Testing for Grubs

• Cut out a 1-square-foot area of sod. Count the grubs in the sod and dirt. Sample four other areas in the yard using the same method to get an idea of the extent of your grub problem. If grubs are only found in one area of the yard, only treat that area. Gardeners who find more than five grubs in a 1-square-foot area should apply a pesticide, according to Michigan State University. Finding fewer than five grubs per square foot means that you can try cultural control options.

Cultural Treatment

• Irrigate new sod more frequently to keep the sod healthy and able to bounce back from grub damage. Avoid allowing sod to dry out by watering with 1 inch of water a week if there hasn't been adequate rainfall. You can tell how much your lawn has been naturally watered by placing cans in the yard. Measure the amount of water in the cans and supplement the rest if there is less than 1 inch.

Chemical Treatment

• Mow the lawn before applying pesticides to help the chemicals absorb into the soil, rather than coating the surface of the grass blades. Water the lawn. Use a pesticide that contains imidacloprid or halofenozide, as recommended by the University of Illinois. Water the lawn after applying the pesticide, so that it can sink into the soil and kill off the grubs. Reapply the pesticide according to the directions. Gardeners may also ask their sod supplier for pesticide after finding evidence of grubs in the yard, as suggested by Michigan State University.