Identification

• The most common type of grub in Illinois is the annual white grub, which is the larva of June beetles. Brown patches of grass in sunny, moist areas may indicate grub damage. Lift up a patch of sod and note the number of grubs present. Ten or more grubs indicates a problem.
  
  

Treatment

• July and August are prime times for larva feeding frenzies, and insecticides are the most effective method for eliminating them. The University of Illinois Extension recommends diazinon, trichlorfon and imidicloprid for grub control. Apply diazinon and trichlorfon in July or August when grubs are present and in the process of causing damage. Imidicloprid should be applied in July when adult beetles lay their eggs.
  
  

Considerations

• Make sure grubs are actually causing the problem before treating a lawn with insecticide. Dryness, poor soil conditions and animal damage can also cause turf injury.
  
  

Prevention

• A lush, thriving lawn is the best defense against grub damage. Following recommended mowing, watering, and fertilization practices will help keep pests at bay, giving grass a chance to stay healthy year-round.