Milky disease of scarabs

Definition

A lethal bacterial infection of scarab beetle larvae (white grubs) caused by Paenibacillus popilliae and related species, characterized by milky-white hemolymph due to massive bacterial sporulation in the body cavity. The disease occurs naturally in soil-dwelling larvae and has been developed as a classical biological control agent, particularly against the Japanese beetle (Popillia japonica) in North America.

Etymology

From the opaque, milk-colored appearance of infected larval hemolymph containing dense bacterial spores.

Example

Application of milky disease spore powder to golf course turf can suppress Japanese beetle grub populations over several seasons, though efficacy varies with soil temperature and moisture conditions.

Synonyms

• Milky spore disease
• Type A milky disease

Related Terms

• Paenibacillus popilliae
• Biological control
• white grub
• Scarabaeidae
• entomopathogenic bacteria
• Japanese beetle

Usage Notes

The term specifically refers to Paenibacillus popilliae infection; distinguish from 'Type B milky disease' caused by Paenibacillus lentimorbus and other Paenibacillus species with similar pathology. Commercial 'milky spore' products contain dried spores applied to soil for long-term grub suppression. The disease is slow-acting and most effective when larval densities are moderate; it does not provide rapid knockdown like chemical insecticides. Natural prevalence varies geographically, with endemic foci in parts of eastern North America.