Wicked Organics Organic Organic OMRI Listed

NPK N/A

Milky spore is a targeted biological control agent that kills Japanese beetle grubs in your lawn and garden — safely, organically, and for up to 10-15 years from a single treatment program. Unlike chemical grub killers that poison everything in the soil, milky spore uses the naturally occurring bacterium Paenibacillus popilliae to specifically infect and kill Japanese beetle larvae without harming people, pets, beneficial insects, earthworms, or plants.

Here’s how it works: when Japanese beetle grubs feed in soil treated with milky spore, they ingest the bacterial spores. The bacteria multiply inside the grub, turning its blood milky white (hence the name), and kill it within about three weeks. As the grub decomposes, it releases billions of new spores back into the soil — creating a self-sustaining cycle that can protect your lawn for over a decade.

Old Cobblers Farm™ Wicked Organics Milky Spore is the organic gardener’s best long-term solution for Japanese beetle grub infestations. One treatment program eliminates the need for annual chemical grub applications, saving money and protecting soil health for years to come.

Application Rates FAQs
Nutrient Profile
WO-MILKY-SPORE
N/A
Derived From
  • Spores of the naturally occurring bacterium Paenibacillus popilliae (Bacillus popilliae)
N/A
NPK Ratio
Organic
Formula Type
3 times per year (spring/summer/fall) for 2 years, then no reapplication needed for 10-15 years
Feeding Frequency
—
Compatible Plants
What It Is

Understanding 0-0-0

Milky spore disease is caused by the bacterium Paenibacillus popilliae, which has been commercially available since the 1940s — making it one of the oldest biological pest control products in use. The bacterium is host-specific, meaning it only infects Japanese beetle grubs (Popillia japonica) and poses no threat to any other organisms.

The granular formulation is applied with a drop spreader over the entire lawn or garden area. For maximum effectiveness, the granular product should be applied three times per year (spring, summer, and fall) for two consecutive years. This builds up the spore population in the soil to levels that provide reliable, long-term grub control.

Milky spore works best when grubs are actively feeding near the soil surface — typically late summer and early fall. Soil temperatures between 60-70°F are ideal for bacterial activity. Results are not immediate — it can take 2-3 years for the spore population to reach effective levels, especially in cooler northern climates.

N
Nitrogen — 0%

N/A — Milky spore is a biological pest control agent, not a fertilizer.

P
Phosphorus — 0%

N/A — No nutrient content.

K
Potassium — 0%

N/A — No nutrient content.

Recommended Plants

Best For

Lawns
Gardens
Flower Beds
Vegetable Gardens
Ornamental Ground Covers
Trees and Shrubs

Growing Detail

Milky spore is primarily used for lawns where Japanese beetle grubs cause brown patches and turf damage. It is also effective in flower beds, vegetable gardens, and around ornamental plantings where grubs damage roots. By reducing grub populations, milky spore also reduces mole and skunk damage — these animals dig up lawns to feed on grubs.
Dosing Guide

Application Rates

Garden Beds
1 lb per 350 sq ft
Container / Pot
N/A — outdoor lawn and garden application only
Water Mix
N/A — apply dry and water in within 24 hours
Lawn
20 lbs per 7,000 sq ft (approximately 3 lbs per 1,000 sq ft)
Trees
Apply granules around the drip line and water in
Per Acre
N/A — primarily a lawn and garden product
Frequency
Every 2-4 weeks

How to Apply

Seasonal Notes

For granular formulation, apply in spring, summer, and fall for two consecutive years. The best results come from fall applications when grubs are actively feeding near the soil surface. Apply when ground is not frozen and soil temperatures are between 60-70°F for optimal bacterial activity. In northern climates like New Hampshire, expect 2-4 years to reach maximum effectiveness.
How It Compares

Side by Side

Milky spore vs. Chemical Grub Killers (GrubEx): Chemical products work faster (within days) but must be reapplied annually, kill beneficial insects, and can contaminate soil and water. Milky spore takes 2-3 years to reach full effectiveness but lasts 10-15 years and is completely non-toxic. Milky spore vs. Beneficial Nematodes: Nematodes work on multiple grub species and act faster but must be reapplied annually. Milky spore targets only Japanese beetle grubs but is self-sustaining.

Safety & Storage

Milky spore is completely non-toxic to humans, pets, plants, and beneficial insects. No special protective equipment is required. Store in a cool, dry location. The product is not affected by freezing or adverse weather conditions. Safe for use in vegetable gardens and around food crops.

Got Questions?

Frequently Asked

  • Milky spore is a naturally occurring biological grub control made from the bacterium Paenibacillus popilliae (formerly Bacillus popilliae). When applied to lawns and gardens, the spores are ingested by Japanese beetle grubs (white grubs) feeding in the soil. The bacteria multiply inside the grub, killing it and releasing billions more spores into the soil. Over 2–3 years, the spore population builds to levels that provide long-term, self-sustaining grub control lasting 10–15 years or more. Old Cobblers Farm™ Wicked Organics Milky Spore is a safe, natural, and permanent solution to Japanese beetle grub damage.
  • Milky spore works by infecting Japanese beetle grubs with the bacterium Paenibacillus popilliae. Grubs ingest the spores while feeding on grass roots in the soil. Once inside the grub, the bacteria multiply rapidly, turning the grub's body fluid milky white — hence the name. The infected grub dies within 1–3 weeks and releases billions of new spores into the surrounding soil. Each dead grub becomes a spore factory, gradually building up the soil's natural defense against future generations of grubs. Old Cobblers Farm™ Wicked Organics Milky Spore provides biological grub control that strengthens over time.
  • Apply milky spore powder by placing 1 teaspoon on the lawn surface every 4 feet in a grid pattern across the treatment area. Water lightly after application to wash the spores into the soil. Apply during the active grub feeding season — late summer through fall when grubs are near the soil surface. The spores need living grubs to multiply and establish, so timing is important. Do not mow for 24 hours after application. One application begins the establishment process. Old Cobblers Farm™ Wicked Organics Milky Spore is easy to apply and begins working as soon as grubs ingest the spores.
  • Once fully established in the soil (typically 2–3 years after application), milky spore can provide effective Japanese beetle grub control for 10–15 years or longer. The spore population is self-sustaining — each infected grub that dies releases billions of new spores, continuously replenishing the soil's biological defense. This makes milky spore one of the most cost-effective and long-lasting grub control methods available. No annual reapplication is needed once the spore population is established. Old Cobblers Farm™ Wicked Organics Milky Spore is a one-time investment in decades of natural grub protection.
  • Yes, milky spore is completely safe for humans, pets, birds, bees, fish, beneficial insects, and all non-target organisms. The bacterium Paenibacillus popilliae is highly specific to Japanese beetle grubs and does not affect earthworms, beneficial nematodes, or other soil organisms. Unlike chemical grub treatments, milky spore poses no risk of poisoning, runoff contamination, or harm to pollinators. It is one of the safest pest control products available. Old Cobblers Farm™ Wicked Organics Milky Spore can be applied to lawns where children and pets play with complete confidence.
  • The best time to apply milky spore is late summer through early fall (August–October), when Japanese beetle grubs are actively feeding near the soil surface. The grubs must be present and feeding for the spores to be ingested and begin the infection cycle. Spring applications can also work if grubs are actively feeding before they pupate into adult beetles. Soil temperatures should be above 60°F for the bacteria to function effectively. Old Cobblers Farm™ Wicked Organics Milky Spore is most effective when applied during the peak grub feeding window in late summer and fall.
  • Milky spore is most effective against Japanese beetle grubs (Popillia japonica), which are the most common and destructive lawn grub species in the eastern United States. It has limited effectiveness against other white grub species like European chafer, Oriental beetle, and June bug grubs. If you are unsure which grub species is causing damage, dig up a few grubs and identify them — Japanese beetle grubs have a distinctive V-shaped pattern of hairs on their raster (rear end). Old Cobblers Farm™ Wicked Organics Milky Spore is the gold standard for targeted, long-term Japanese beetle grub control.

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