Lawn infested with grubs
I live in Georgia VT and have a large lawn. The soil is sandy and has large bare spots. I can see those ugly white grubs in the soil. Can I spread grub klller now or when is the best time? Do I need a special kind of grub killer?
Hi Vermont Lawn Person
Here is a link to identifying grubs:
Beneficial Nematodes are an option. Here is some information on that:
University of Maine Cooperative Extension
Using Beneficial Nematodes for Grub Control Nematode Biology
Nematodes are microscopic, non-segmented worms which occur naturally in soil all over the world.
Thousands of strains exist with different lifestyles. Beneficial nematodes attack only soil-dwelling insects
and leave plants alone. Beneficial nematodes and the bacteria they spread are not known to be harmful to
humans, animals, plants, earthworms and other non-target organisms, but they do aggressively pursue
insects like grubs. When they sense the temperature and carbon dioxide emissions of soil-borne insects,
beneficial nematodes move toward their prey and enter the pest through its body openings. The
nematodes carry an associated bacterium (Photorhabdus species) that kills insects fast (within 48 hours).
Several generations of nematodes may live and breed within the dead pest; they emerge and seek more
pests in the soil. Beneficial nematodes have been shown to be as much as 96% effective against Japanese
beetle grubs in field studies.
Nematode Use Guide
Although many species of beneficial nematodes are available, Heterorhabditis bacteriophora (Hb)
nematodes are most effective against Japanese beetles, European chafers and other grubs that are lawn
pests. They are more efficient than the Steinernema carpocapsae. Hb nematodes work better because
they are cruiser nematodes that burrow down in the soil searching for deep soil-dwelling pests. They also
have a special “tooth” that helps them get into the grub.
Nematodes are shipped in the infectious juvenile stage of their life cycle and can be stored in the
refrigerator for up to 2 - 3 weeks. They may come on a sponge, in gels, granules or liquids.
The best time to apply nematodes depends on the weather and grub species. Most summers mid to late
August is about right. The grubs should be actively feeding and in their second or third instar when they
have larger spiracle openings. The nematodes enter the grubs through the spiracles, mouth and anus and
release a fungus which then consumes the grubs.
The nematodes are neutralized by exposure to strong sunlight, so they must be applied in heavily overcast
or rainy conditions; at dusk or during rainfall is an ideal time. Nematodes prefer a moist environment. If
the ground is very dry, it helps to pre-irrigate the area with at least 0.5 inches of water.
Follow the label and mixing instructions carefully. To treat a 2000 sq. ft. lawn area, mix 1 million
nematodes in at least 4 gallons of water that is under 86o F. Carefully pour the nematodes into a hand
sprayer, hose-end sprayer or pressurized backpack sprayer and use the spray solution immediately. The
sprayer nozzle opening should be at least 0.02 inches and any screens should be removed. Evenly spread
the solution over the area to be treated. Continuous mixing should take place to prevent the nematodes
from sinking to the bottom. After application apply 0.25 inches of water to wash the nematodes off the
grass blades, and then keep the soil moist for at least two weeks to help them get established.
After treatment, monitor the lawn carefully. If grub damage continues, apply nematodes a second time.
Infected grubs take on a brown appearance (see below).
Where to Purchase Beneficial Nematodes
Company Name Company Location Contact Information
The Green Spot Ltd. 93 Priest Rd, Nottingham, NH
O’Donal’s Nursery 6 County Road, RFD #4, Gorham,
North Country Organics P.O. Box 372, Depot Street
Bradford, VT 05033
Skillin’s Greenhouses 89 Foreside Road - Falmouth,
Fedco Seeds PO Box 520, Waterville, ME
Hydro-Gardens P.O. Box 25845
Colorado Springs, CO 80936-5845
Griffin’s Greenhouse &
50 West Gray Road
Gray, ME 04039
Hope this information is useful to you, let us know if you have any other questions.
UVM Extension Master Gardener Volunteer