In the late summer my lawn has become infested with Japanese beetle grubs. Now the turf is being dethatched very efficiently by crows. I want to prevent re-infestation next spring without using poison; I don't want to poison the birds. Every neighbor has stopped by to advise me to pour diazinon on it. We'll have a freeze any day now, so I'm not going to do anything but clean up for the winter. Two questions: 1) What can I use in spring to combat the problem? and (2) If I put a perennial border instead of grass in that area will the grubs destroy their roots as well? Thanks for any ideas or sources you can provide. 
Do not fret, there is an organic solution to your problem. Japanese beetle grubs can be killed by milky disease bacteria. This disease (which falls into the organic range) will infect and kill the grubs of the Japanese Beetle and its close relatives. The disease will remain in the soil for many years, so you don't have to worry about repeat treatments. First, you have to find and order the bacteria (scientific name: Bacillus popilliae and Bacillus lentimorbus) from an online organic gardening catalogue (This site sells milky disease spores). Then, you want to follow the directions that come with the bacteria and spread it on your lawn. It may take 2 to 5 years to remove all grubs from your lawn, but you can be sure that the grubs will not return anytime soon. For more information on the milky spore bacteria, visit St. Gabriel Laboratories.
Nematodes, also called eelworms, can also be used to control Japanese beetle grubs. Nematodes are microscopic, slender,
translucent roundworms. They live in moist areas such as soil, decaying
organic matter, water, and the insides of other animals. Parasitic nematodes
kill Japanese Beetle grubs. Make sure that you purchase the correct type
of nematode, because there is a tremendous diversity of species (and not all are
beneficial in the garden). For more information about nematodes, visit this website on parasitic
nematodes.
To kill mature Japanese Beetles, purchase a Japanese Beetle trap at your local garden supply store. These traps, which lure the beetles with a scent, are extremely effective.
About a perennial border instead of grass: grubs will attack perennials too, but the perennials will have a much better chance of surviving the grubs than grass.
How do I organically keep Japanese beetles from destroying my rose
bushes? Since they live in the soil, spraying the bushes does not work. 
Japanese beetle traps can be purchased at your local garden supply store. These plants use pheromones (insect sex scents) to lure the beetles into the traps. They are extremely effective and are considered organic. If you want to find out more about Japanese beetles, grubs (Jap beetle pupae), or other methods of control (like milky disease spores), click here.
Moles are digging up my garden! How can I get rid of them organically? 