Tasmanian grass grub (Aphodius tasmaniae) are dark brown or black beetles around 10mm (1/2 inch) long. As adults, they are attracted to dung and lay their eggs there. The larvae feed on the dung for four to six weeks and then move onto the pasture, where they eat all foliage in sight. This creates large bare patches. Knowledge of how to control these grubs will help you keep up a healthier lawn.
Look for areas of defoliation and inspect the ground for small tunnels 1/4 inch (3 to 5 mm) in diameter. These are the emergence tunnels of the grubs. In periods of heavy rain or hard frosts, they will stay in the ground, creating a larger problem.
Make sure that you are dealing with the Tasmanian grass grub and not the black beetle. They both look similar, but the Tasmanian grass grub has a ridged back. Each beetle requires different control tactics.
Apply an insecticide containing pyrethroid at the first signs of infestation. This is a synthetic compound that will work well to control the grubs. Follow the directions on the label carefully for application instructions.
Apply the insecticide again if problems persist. The Tasmanian grass grub may require a few applications to kill them off completely.