If you’re battling grubs in your lawn, you might be wondering what does milky spore kill. This natural bacteria is famous for its effectiveness against Japanese beetle grubs, offering a long-term solution for gardeners. It’s a safe, organic method that targets specific pests without harming your plants, pets, or beneficial insects. Let’s look at how it works and how you can use it.
What Does Milky Spore Kill
Milky spore is the common name for a bacterium called Paenibacillus popilliae. It’s a naturally occuring soil organism that causes a disease known as milky disease in certain grubs. When a susceptible grub eats the spores, they multiply inside its body, eventually turning its fluids a milky white and killing it. As the grub decomposes, it releases billions of new spores back into the soil.
Primary Target: Japanese Beetle Grubs
The primary and most effective target of milky spore is the larval stage of the Japanese beetle (Popillia japonica). This is what it’s famous for.
- Japanese beetle grubs are C-shaped, white, and live in your soil, feeding on grass roots.
- This damage causes brown, dead patches in your lawn that can be peeled back like loose carpet.
- Milky spore provides a multi-year control cycle, building up in your soil over time.
Other Susceptible Grub Species
While Japanese beetles are the main target, research shows milky spore can also infect and kill a few other closely related beetle grubs. The effectiveness can vary.
- Some chafers (like the northern masked chafer).
- European chafer grubs (though this is less consistent).
- Oriental beetle grubs.
What Milky Spore Does NOT Kill
It’s crucial to understand its limits. Milky spore is highly specific. It will not harm:
- Adult Japanese beetles or other adult insects flying around.
- Other common lawn grubs like Billbugs or Armyworms.
- Earthworms, bees, ladybugs, or other beneficial creatures.
- Pets, wildlife, or people.
- Your grass, flowers, vegetables, or any plants.
How to Apply Milky Spore for Best Results
Proper application is key to establishing milky spore in your soil. Follow these steps for success.
1. Timing is Everything
Apply milky spore when grubs are actively feeding near the soil surface. The best times are:
- Early spring (once soil temperatures reach about 60°F).
- Late summer to early fall (mid-August through October).
- Avoid applying in the heat of mid-summer or when the ground is frozen.
2. Preparation and Tools
You don’t need much. Get a milky spore powder or granular product. You’ll also need a standard lawn spreader for granular form or a special applicator for the powder. Lightly water your lawn a day before if it’s very dry.
3. The Application Process
Here is a simple step-by-step guide.
- Mow your lawn to a normal height.
- Fill your spreader or applicator with the milky spore product.
- Apply it over your entire lawn, walking in a grid pattern for even coverage. Don’t worry about spreading it in garden beds where grubs aren’t a problem.
- Water the lawn lightly after application to wash the spores into the soil. A quick 1/4 inch of water is perfect.
4. Aftercare and Patience
Do not use chemical insecticides on treated areas, as they can kill the spore. You can continue to water and fertilize your lawn normally. Remember, milky spore is not an instant fix. It takes 1-3 years to build up enough in the soil to see significant grub reduction. You only need to apply it once every 10-20 years after its established.
Integrating Milky Spore into a Complete Pest Strategy
Because milky spore only kills grubs, you need other methods for adult beetles.
For Adult Japanese Beetles
- Hand-pick them early in the morning when they are sluggish. Drop them into soapy water.
- Use pheromone traps, but place them far away from your prized plants, as they can attract more beetles to your yard.
- Apply neem oil or insecticidal soap to affected plants as a deterrent.
- Plant Japanese beetle-resistant varieties like boxwood, lilac, or magnolia.
For a Healthy, Grub-Resistant Lawn
- Water your lawn deeply but infrequently to encourage deep root growth.
- Mow high, keeping grass about 3 inches tall.
- Aerate your soil annually to reduce compaction.
- Use a balanced, slow-release organic fertilizer.
Common Mistakes to Avoid
Even experienced gardeners can make a few errors with milky spore.
- Applying at the wrong time of year when grubs are too deep.
- Expecting immediate results within a single season.
- Using chemical pesticides alongside it, which counteracts its work.
- Applying it to a very small area. It works best when neighbors use it too, creating a community-wide effect.
FAQ About Milky Spore
Is milky spore safe for my dog?
Yes, it is completely non-toxic to mammals. Your pets can use the lawn immediately after the light watering-in period.
Can I use milky spore in my vegetable garden?
You can, but it’s usually not necessary. Japanese beetle grubs primarily feed on grass roots, not vegetable plant roots. The application is typically for lawns.
How long does a milky spore treatment last?
Once successfully established in your soil, milky spore can remain effective for 15 to 20 years. It’s a one-time investment for long-term control.
Will heavy rain wash away the milky spore?
A light watering helps it soak in, but a torrential downpour immediately after application could wash it away. Check the forcast and try to apply when mild weather is expected.
Can I apply milky spore and grass seed at the same time?
Yes, you can. They will not interfere with each other. Just follow best practices for seeding, like keeping the soil moist for germination.
Why haven’t I seen dead grubs after applying milky spore?
The grubs die underground. You won’t typically see them on the surface. The evidence of success is a reduction in lawn damage and fewer adult beetles over the years.
Making the Decision: Is Milky Spore Right for You?
Milky spore is an excellent, eco-friendly choice if Japanese beetle grubs are your confirmed problem. It requires patience and an upfront effort, but it pays off with decades of control. For other types of grubs, you may need to identify the pest correctly and consider other organic options like beneficial nematodes. Start with a soil inspection to confirm the presence of Japanese beetle grubs. If you find them, milky spore can be a powerful ally in reclaiming your green, healthy lawn without resorting to harsh chemicals. The key is to set realistic expectations and combine it with other smart gardening practices for the best overall results.