Protecting Roses from Japanese Beetles: Milky Spore & Quick Action Tips

If you’ve ever watched your beautiful rose blooms get skeletonized seemingly overnight, you’ve likely met the Japanese beetle. These shiny, copper-green pests are not only voracious feeders—they also invite more beetles to the party by releasing pheromones as they feed.

One effective, long-term solution? Milky Spore.

What Is Milky Spore?

Milky Spore is a naturally occurring bacterium (Paenibacillus popilliae) that targets Japanese beetle grubs in the soil. When applied correctly, it works as a biological control, infecting the grubs that hatch underground before they emerge as adult beetles.

• How to Apply: Use a drop spreader or scoop to apply the powder to your lawn in a grid pattern.

• When to Apply: Best applied from spring through early fall, when soil is warm and grubs are active.

• Bonus: Milky Spore is safe for people, pets, pollinators, and beneficial insects.

It takes time—often 1–2 years—for Milky Spore to establish and provide widespread protection, but once active, it can persist in the soil for up to 15 years.

What to Do If You Already See Japanese Beetles on Your Roses

While Milky Spore works underground, here’s how to protect your roses above ground:

1. Handpick and Drown:
In the early morning when beetles are sluggish, gently shake or pick them off into a bucket of soapy water. It’s simple and effective.

2. Skip the Beetle Traps:
Those traps attract more beetles than they catch—often worsening the problem. Avoid placing them near your rose garden.

3. Cover Delicate Plants:
Use floating row covers during peak beetle season to physically block access to your roses.

4. Neem Oil Spray:
Neem oil can help deter feeding. It’s best used early and often (but never in direct sunlight, as it may burn the leaves).

5. Encourage Natural Predators:
Birds, tachinid flies, and nematodes can all help reduce beetle populations. A healthy, biodiverse garden is your best long-term defense.

With a combination of preventive soil treatment and quick above-ground action, you can reduce Japanese beetle damage and keep your roses blooming beautifully.