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University of Illinois Extension serving Bureau, LaSalle, Marshall and Putnam Counties

Main Office (Bureau County)
850 Thompson St,
Becker Professional Suites,
Princeton, IL 61356
Phone: 815-875-2878
FAX: 815-875-2870
Hours: Monday-Friday 8:00am to 4:30pm (Closed 12 - 1pm)

Branch Office (LaSalle County)
1689 North 31st Road,
Suite 2
Ottawa, IL 61350
Phone: 815-433-0707
FAX: 815-433-5454
Hours: Monday-Friday 8:00am to 4:30pm (Closed 12 - 1pm)

Branch Office (Marshall County)
509 Front Street,
Suite 4
Henry, IL 61537
Phone: 309-364-2356
FAX: 309-364-2804
Hours: Monday-Friday 8:00am to 4:30pm (Closed 12 - 1pm)

News Release

Milky Spore Frequently Asked Questions

Milky Spore Frequently Asked Questions

What is Milky Spore?

Milky Spore is a naturally occurring bacterium that affects only Japanese Beetle.

How fast does it work and how long does it last?

Milky Spore begins working as soon as it is applied as long as grubs are feeding. Once grubs are infected they will multiply the Spore by several billion times and spread it further. In warm climates good control can occur in one to three years. Once established in a lawn, Milky Spore has been known to last 15 to 20 years.

Will freezing ruin the Spore? What about heavy rain?

No, Milky Spore is not affected by freezing or other adverse environmental conditions. Heavy rain may wash away newly applied Spore dust necessitating retreatment.

Can I use Milky Spore in the vegetable garden?

Yes, Milky Spore is harmless to food crops. It is not a chemical pesticide. It may be used in gardens, around pools and wells.

Should children and pets be kept off the treated lawn?

Milky Spore does not affect pets, beneficial insects, fish, bees, birds, other animals, plants, or man. It is not a poison.

Can I mix the Spore in water and spray it?

No, the Spore dust must remain concentrated and applied in spots. DO NOT apply Milky Spore Powder with fertilizer spreaders or grass seed spreaders.

Can I cut my grass after applying the Spore?

NO. DO NOT MOW your grass until the Spore has been watered into the soil by rain or hose for 15 minutes or longer.

What if I treat my yard and my neighbor doesn't?

Your lawn will be protected even if you are surrounded by untreated property. Eventually, the Spore may creep next door into adjacent areas by natural movement.

Won't beetles fly in front of my neighbor's yard?

An adult beetle feeds only during its first two weeks. By the time they fly in from adjacent areas, any grubs laid will be affected by the Spore.

What about moles?

Eliminating grubs with Milky Spore may cause moles and skunks to feed elsewhere. Unfortunately, they may head for your neighbor's untreated yard instead. Milky Spore does not affect moles; it simply reduces their food source.

Can I have too many grubs?

If you are rapidly losing your lawn due to too many grubs, more than 10 per square foot, you may be wise to use an insecticide along with Milky Spore.

How do I know if I have beetle grubs?

Grubs feed on the roots of your grass which can become brown and die. Simply lift the dead grass and look for white larvae curled into the shape of a "C" about the size of a penny. Active grubs can completely destroy a lawn. Use Milky Spore for safe, long-lasting control.

Do beetle larvae feed more aggressively in fall?

Yes, grubs in fall are the first instar stage and are feeding for growth to store body fat for winter. In the spring, grubs reach 3rd instar prior to molting and do not require as much food.

Are grubs infected by Milky Spore in spring when rising to the surface following hibernation?

Grubs become infected by swallowing a spore. They do not become infected by rubbing up against spores or passing through them. Since grubs feed less in spring, the incidence of infection is not as great in fall.

What are the application rates for Milky Spore?

Milky Spore powder must be applied in teaspoon amounts every four feet in rows four feet apart creating a grid pattern. Water it in good.

What is the shelf life of Milky Spore?

Milky Spore has unlimited shelf life as long as it is stored in a cool dry place.

What if I get Milky Spore in my eyes?

What if I breathe it in?

No cause for concern. Milky Spore is not a chemical pesticide. The only thing that Milky Spore affects is Japanese Beetle Grubs.

For more information, contact Paul Barrett, LaSalle County Master Gardener Coordinator at (815) 433-0707 or e-mail him at

Local Contact: Paul Barrett, Master Gardener/Master Naturalist Program Coordinator,