Turf - Grub Control With Beneficial Nematodes

The following is information on grub control in lawns using beneficial nematodes from the University of Maryland.

Non –Chemical Control of Grubs in Lawns

The interest in non-chemical control of white grubs in lawns is increasing. Japanese beetles are laying eggs in the soil in late July through early August. The newly hatching larvae will be very susceptible to control using beneficial nematodes. Nematodes are microscopic, non-segmented worms which occur naturally in soil all over the world. Beneficial nematodes attack soil dwelling insects and leave plants alone. These predators enter the host through body openings or by penetration of the body wall. Beneficial nematodes are considered safe and EPA has waived the registration requirements for application.

When Heterorhabditis bacteriophora (Hb) nematodes sense the temperature and carbon dioxide emissions of soil-borne insects, they move toward their prey and enter the pest through its body openings. The nematodes carry an associated symbiotic bacterium (Xenorhabdus species) that kills insects within 48 hours. The bacteria is harmless to humans and other organisms and cannot live freely in nature. Several generations of nematodes may live and breed within the dead pest before emerging and seeking more pests in the soil.

Heterorhabditis bacteriophora nematodes are a good choice for white grub control at this time of year. The key is that they need a lot of water to survive in turf areas. Irrigate the day of the application or apply during periods of rain. The lawn area must be keep moist for a couple of days after an application to keep the nematodes alive. Infected grubs become slimy and discolored and turn from white-beige to red-brown within 3 to 5 days after application. Nematodes leave the grub when they reach the infectious third stage to search for new larvae. The nematode population will slowly decrease when no new hosts are present.

Checking to Make Sure Nematodes Are Alive is Essential: It’s critical when using beneficial nematodes to check the population to make sure they are alive at application time. Draw off a small sample and examine the water with nematodes under a magnification of 20X. Live nematodes will be slightly curved and moving. Dead nematodes are still and straight as a board.

Information from Stanton Gill, University of Maryland http://www.ipmnet.umd.edu/09Jul24L.pdf