Effective Grub Control for Reseeding: Beyond Milky Spore to Beneficial Nematodes

Effective Grub Control for Reseeding: Beyond Milky Spore to Beneficial Nematodes

Zip 19380 (PA). Milky spore didn’t work two falls ago. You want to overseed this spring and need grub control that actually works. Milky spore only kills Japanese beetle grubs—and slowly.

Why Milky Spore Failed

• It’s specific to Popillia japonica larvae. Other grubs (masked chafer, European chafer) are unaffected.
• Incubation takes years. Infected grubs still damage roots before dying.
• Some strains show resistance; commercial formulations vary in viability.

The Winner: Steinernema kushidai Nematodes

A 2000 study (Cornell, BioOne) compared Bt, milky spore, Diazinon, and nematodes. Steinernema kushidai killed grubs in 24–48 hours—the only treatment with that speed. It also hits termites, fleas, fungus gnats.

Where to Get Them

Not sold in US retail yet. Best lead: Natural Insect Control (Canada). They may source S. kushidai or recommend a climate-appropriate alternative (e.g., Heterorhabditis bacteriophora).

Address the Root Cause

Grub explosions often follow soil disturbance (new construction) that wiped out natural predators (starlings, ground beetles, parasitic wasps). Avoid broad-spectrum insecticides. Build soil health to restore the food web.

Milky spore is a lottery ticket. Nematodes are a sniper. Aim for the sniper.