Milky Spore Disease, "Paenibacillus papillae", is a passive means of control of Japanese Beetles and is not very effective against other members of the Scarab Beetle family. The grubs must find and then ingest the spores which then grow and eat the grubs insides turning them into the distinct milky white color that gives the disease its common name. The grubs die but do not explode, and the bacterium that killed them reverts to spores (dormant stage) until some other grub ingests those spores and the cycle starts over.

The most effective time to control grubs in the lawn is August and September while I see most controls being peddled in May and June. The most effective means of control is to grow a good healthy lawn in a soil well endowed with organic matter that is evenly moist but well drained with the soil pH in the optimal (6.0 to 7.0) range and balanced nutrients.

http://ento.psu.edu/extension/factsheets/white-grubs-lawns

kimmq is kimmsr