Milky Spore for Lawn Grub Control

The short answer is: NO.

The long answer is: Milky Spore is a product that contains spores of a strain of the milky disease-causing bacterium Paenibacillus popilliae. The strain was isolated from and is produced in larvae (white grubs) of the Japanese beetle (Popillia japonica). Strains of this bacterium and the closely related Paenibacillus lentimorbus are rather host-species specific, meaning they rarely infect other white grub species. Hence, the strain in Milky Spore will primarily infect larvae of the Japanese beetle, maybe the occasional oriental beetle (Anomala orientalis) larva, but nothing beyond that. Larvae of the oriental beetle, masked chafers (Cyclocephala species), green June beetle (Cotinis nitida), Asiatic garden beetle (Maladera formosae), and May beetles (Phyllophaga species) will therefore not be affected significantly by Milky Spore.

Field data on the efficacy of Paenibacillus popilliae preparations, especially of Milky Spore, are rare and generally do not show a significant effect of applications on Japanese beetle larval populations. Nonetheless, natural populations of Paenibacillus popilliae can have a significant impact on white grub populations. However, for a natural population to establish and persist, two factors are important: a significant number of Japanese beetle larvae need to be present so that the disease can infect enough hosts and multiply in them, and soil temperatures should be above 70°F for several weeks.

Take home message regarding Milky Spore:

• Only use if the target white grub population consists primarily of Japanese beetle.
• Do not expect high efficacy.
• If the disease establishes, it might take several years to spread through the entire treated area.