An entomologist at a turfgrass conference I attended didn't think milky spore was worthwhile. Quoting from a Cornell University article, "..... a recent field study in Kentucky showed that commercial formulations of
P. popilliae (milky spore disease) were only moderately infective (39-44%), that infected grubs consumed the same amount of roots as uninfected grubs, and that lower grub populations could not be linked to infection. Researchers concluded that earlier reports of success were limited to very high infestations of grubs where other stresses may have increased their susceptibility to diseases." This is from:
http://www.biocontrol.entomolo...
In the talk I was at, the beneficial nematode
Heterorhabditis bacteriophora was said to be a better choice among the organic treatments.
Another problem with milky spore is that it only targets Japanese beetles, whereas there are many other kinds of related "white grubs". You can tell the difference between these grubs by looking at the raster spine arrangement on their bottoms and comparing with diagrams of the spine pattern, but getting them to stay uncurled while peering at their posteriors can be a challenge, especially with the smaller ones. Here's one such guide to raster patterns:
http://www.msuent.com/assets/p...
