Lawn infested with grubs

Asked May 20, 2019, 7:36 PM EDT

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?

Vermont

1 Response

Hi Vermont Lawn Person

Here is a link to identifying grubs:

https://ohioline.osu.edu/factsheet/hyg-2510

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

03290-6204

603-642-8925

www.greenmethods.com

O’Donal’s Nursery 6 County Road, RFD #4, Gorham,

ME 04038

207-839-4262

www.odonalsnurseries.com

North Country Organics P.O. Box 372, Depot Street

Bradford, VT 05033

802-222-4277

www.norganics.com

Skillin’s Greenhouses 89 Foreside Road - Falmouth,

04105

207-781-3860

www.skillins.com

Fedco Seeds PO Box 520, Waterville, ME

04903

207-873-7333

www.fedcoseeds.com/ogs.htm

Hydro-Gardens P.O. Box 25845

Colorado Springs, CO 80936-5845

888-693-0578

www.hydro-gardens.com

Griffin’s Greenhouse &

Nursery Supplies

50 West Gray Road

Gray, ME 04039

207-657-5442 www.griffins.com

Hope this information is useful to you, let us know if you have any other questions.

Mary Ann

UVM Extension Master Gardener Volunteer