Lawn grubs are the offspring of beetles, chafers and other lawn dwelling bugs. White grubs feed on the roots of grass as they grow, creating weakened foliage that easily pulls up from the lawn. An indications of a lawn grub infestation is brown and patchy grass. Grass shows symptoms of lawn grub damage in the spring, after most of the damage is done in the fall. When grubs are at a number of five per square foot in low maintenance lawns, or 15 to 20 grubs per square foot in high maintenance lawns, control measures are required.
Cut a square around an area of turf where there is potential grub damage using a knife and peel back the turf with a spade. Count the grubs in the area to determine whether you are at the threshold for grub infestation.
Take samples from your lawn in areas where lawn grubs are expected, to capture the grubs for identification advises the University of Rhode Island. Send the grubs to a local university extension office for identification.
Reduce the amount of water you give the lawn in late July and early August to prevent bugs from laying eggs in your lawn recommends the University of Missouri. Most grub laying bugs require moisture in the soil to lay their eggs.
Apply a preventative pesticide between August 1st and September 15th to prevent bugs from laying their eggs. Diazinon2, ethoprop3, trichlorfon4, bendiocarb5, halofenozide, and carbaryl are common chemicals used for the control of grubs. Apply according to the bug species, following the instructions on the label of the insecticide container.