Since the arrival of the Japanese Beetle in North America, it has proved difficult and expensive to control. The larvae feed on the roots of grasses from underneath the soil out of reach of many potential enemies. The larvae do have diseases including Paenibacillus popilliae a bacterium that can reproduce in the hemolymph. Hemolymph of infected larvae has a “milky” appearance and called milky spore disease or milky spore bacteria. In 1933, Milky spore became the first microbial insect control product registered in the US.
The disease only thrives when soil temperatures reach the 66 to 70 degree F range. For northern states such as Indiana, the adults may emerge before the soil temperature is warm enough for the bacterium to grow effectively. It does not supply complete control, but under favorable conditions, can suppress the Japanese beetle population.
Paenibacillus popilliae is difficult to culture in artificial broth and is produced commercially from infected larvae. In the mid 1980s a company patented a method of producing Paenibacillus popilliae in culture but the bacteria being produced were Paenibacillus polymyxa not P. popilliae. Commercial manufacture of milky spore has returned to the original method and little progress has been made with culture. Now that DNA fingerprint techniques for identifying P. popilliae. are available perhaps some progress could be made. The fingerprinting would help guard against culturing the wrong organism.