Dave Smitley, Entomology

All the rain we had this summer has stopped and lawns in much of the state are looking dry. Dry weather in late September and October is when we are most likely to see grub damage. The reason for this is that a infestation of greater than 10 grubs per ft2 can consume more than 50 percent of all the turf roots in a lawn. As long as the soil remains moist and fertility levels are adequate, the turf plants will continue to grow new roots and take-up enough water. However, in very dry soil the turf plants stop growing and more than 50 percent root loss compromises uptake of enough water to keep the stressed plants alive. Consequently, turf plants will begin to die. The grubs don’t mind, because they will eat the dead turf roots and stems as well as live ones.

Watch for developing patches of dead turf in dry lawns. Sample these areas with a cup-cutter or shovel. A cup-cutter removes and area equal to about 1/10 ft2 and a shovel with a six inch-wide blade will make a square area of ¼ ft2. Take samples and determine how many grubs are present. With five or less per ft2 frequent watering is all that is needed. With more than 10 per ft2, treat the infested areas with Sevin or Dylox and water frequently to keep the soil moist until November.


Grub damage in Dewitt, MI.


Grub damage on MSU's campus.