Damage

• Grubs are the larvae of a variety of beetle species, including the Japanese beetle. Typically small and white, grubs and have distinctive c-shaped bodies, according to the University of Illinois Extension. The larvae feed on the roots of plants, preventing the plants from taking in nutrients and weakening the plants rapidly. The presence of grubs makes garden plants and lawn grass more susceptible to disease and other insect pests.
  
  

Preventative Care

• Plants are available that can be used to prevent adult beetles from feeding and mating in the garden, which leads to grubs the subsequent year. According to North Dakota State University, evergreens repel the Phyllophaga implicita or horn beetle, keeping these insects from entering a garden or lawn. Plant garden plants that are tolerant to grub problems; sunflowers help to reduce grub damage.
  
  

Tilling

• Tilling helps control the population of grubs before they can hatch. Turning up the soil in the garden exposes the beetles' eggs to the open air, sunlight and pesticide applications, which helps reduce the number of grubs that are capable of hatching. Till the garden annually to help uproot any existing grubs and kill them. Till in early spring, before the grubs hatch.
  
  

Pesticides

• The application of pesticides is key to controlling a grub population if larvae are present in the garden. Choose a pesticide designed for grub control, and apply it to the garden as often as necessary. Follow all directions on the pesticides. Excess chemicals can become damaging to garden plants and build up a residue that is environmentally harmful. Pesticides are useful for controlling grubs when preventative measures fail.