Testing is accomplished by sectioning off the lawn and making a map of the area. A cup cutter is used to remove a sample of sod to a depth of about 4 inches. Soil is removed from the sod and physically looked at for grubs. If there is greater than 10 grubs per square foot, then that area might be treated depending on condition of the turf. Only areas of high concentration of grubs would be treated. The soil and sod are replaced and should be watered after the test.
Heterorhabditis bacteriophora (Hb) nematodes are used for grub control; they are colorless, unsegmented, parasitic, very small roundworms. To see them, a 10 time’s magnifying glass is required. Normally there are always a small number of these beneficial microscopic worms present in soil. They feed and reproduce within the grub’s body, producing 10’s of thousands more nematodes, which are ready to search and destroy more grubs.
The only proper time to treat for grubs is mid to late August when the grubs are very small and basically no lawn damage has occurred. Treating in late September or in spring is less effective in killing the grubs and damage to the lawn has already happened. Hb nematodes would be applied in overcast weather, during a light rain, or at dusk to minimize ultraviolet radiation. They do best in moist soil that is not allowed to dry completely,( but not in swampy soils).
Hb nematodes are completely harmless to people, pets, and plants by ingestion or injection. Unlike chemicals, Hb nematode applications do not require mask or other safety equipment and re-entry time, residues, ground water contamination are not issues. There is no phytotoxicity (being poisonous to plants). The US Environmental Protection Agency has exempted them from registration required for chemicals.