Is Milky Spore Safe for Humans When Used on Lawns to Control Grubs?

Japanese beetle grubs are a common pest in lawns.

Milky spore, derived from the bacterium P. popilliae, is a microbial insecticide used to control grubs of the Japanese beetle. Because the bacterium only affects the target species, it does not harm other insects, animals or humans, according to Cornell University.

History

Japanese beetles are an invasive species of beetle in the United States because they have no natural predators. In the 1930s, scientists discovered that milky spore bacteria, which cause milky disease in beetle grubs, naturally controlled Japanese beetle populations in the United States.

Toxicity

Milky disease causes toxicity to Japanese beetle grubs when applied to lawns. This occurs as the beetles feed on the roots of infected grass after milky spore application, reports Penn State University. The disease is toxic only to Japanese beetle grubs, however, not humans.

Effectiveness

When first introduced, milky spore decreased Japanese beetle populations by 41.5 percent, but since then the beetles have grown resistant with only .2 percent effectiveness, Cornell University reported. Penn State University states when infected grubs die, they can release up to 2 billion P. popilliae spores back into the soil, but the process can take one to two seasons before it is effective for grub control.

References

• Cornell University: Milky Disease
• Penn State University Live: Take Control of Grubs in Your Lawn
• University of Rhode Island Landscape Horticulture Program: White Grub Control