Beneficial Nematodes to Control Lawn Grubs

Grubs, the larval stage of beetles, eat the root system of lawns.

Grubs are the larval stage of many types of beetles. They live in soil and feed on the root system of lawns. This causes significant damage to the lawn. Chemical pesticides are effective in controlling grubs, but they must be applied when the grubs are small and are close to the surface of the lawn. Many people do not want to use pesticides. Beneficial nematodes are an environmentally safe way to control lawn grubs.

Features

Nematodes are among the most numerous multicellular organisms. They are small, parasitic roundworms that naturally occur in soil. Although they live in soil of lawns, not enough nematodes are present for adequate grub control. Beneficial nematodes, or predator nematodes, can be applied to turf lawns to control grub populations.

Function

Beneficial nematodes migrate through soil, looking for host grubs. They find them by detecting carbon dioxide and other chemicals that are emitted by grubs. Once they locate a grub, they enter the grub and release a symbiotic bacterium. Nematodes enter the grub through the natural openings of the grub or pierce its body using their hooklike mouth to create an entrance. The bacterium kills the grub within 24 to 48 hours. Nematodes remain in the dead grub and multiply. In 12 to 14 days, the nematodes leave the dead grub and move through the soil, looking for new hosts. This cycle is repeated over and over, and it provides effective grub control.

Types

Two specific types of nematodes are effective against grubs. They are Steinernema and Heterorhabditis. Steinernema is the most widely available beneficial nematode. Heterorhabditis is very effective against white grubs, but it is more susceptible to environmental extremes. It cannot be applied in areas with consistently high temperatures.

Application

Beneficial nematodes are sold in powder or granule from and are mixed with water according to the specific product's directions. They are applied using a hose-end sprayer or pump sprayer. The nematodes in the powder or granule form can be stored for up to one month in a refrigerator. Once they are mixed with water, they must be applied immediately. The nematodes must be supplied with adequate water before and after application. This will help them travel deep into the soil to locate grubs.

Considerations

Beneficial nematodes are an environmentally safe biological treatment to control lawn grubs. Although the bacterium that they produce is fatal to grubs, they pose no threat to humans, wildlife, pets or water sources.

References

• Colorado State University Extension: Insect Parasitic Nematodes
• Texas A&M University System, AgriLife Extension: White Grubs in Texas Turfgrass
• University of Wisconsin, "Midwest Biological Control News;" The Nematode Heterorhabditis Bacteriophora; Susan Mahr; November 1999