There are a lot of great products out there for controlling insect pests without using pesticides. Some of the best include insect diseases or predators which will attack the pest and not beneficial. For example, there are wasps that kill mealybugs and nematodes that attack grubs. Both of these products are pretty effective. That said there are also some products that just don’t work that well. One of them is known as milky spore disease.
Milky spore disease is a bacteria that infects a variety of different scarab beetles – of which the Japanese beetle is one. It isn’t a disease that we imported from Japan – it’s actually one that was found here. Because this disease affects the Japanese beetle and it isn’t a pesticide per se people get very excited about it. The problem is that it just doesn’t work that well. Sure, it will offer some control, but not much. Probably somewhere less than 20%. Furthermore, most people use it in hopes of reducing their adult beetle population, but adult beetles come from all over, perhaps even miles away, so killing the beetles in your soil doesn’t in any way guarantee that you’ll be controlling the adult beetles eating your roses.
Now if you want to encourage your township to try milky spore disease that might work. Spread over larger areas milky spore will have more of an effect for obvious reasons. But placed on one yard, it’s just not going to do that much.
The thing about anecdotal deductions is that to the person making them they seem very logical and legitimate. I had a terrible problem with Jap. Beets on my property for several seasons and about 15 years ago spread some milky spore. The following year the problem was notably less and by the year after that and ever since, they’re barely here at all.
Some time back the research from Cornell suggested MS was as affective as any soil applied chemical control but now researchers suggest that JB.s fly from elsewhere even if you get some control in your own soil. That is strange to me, because I have a site I manage with two separate orchards of over 50 mature fruit trees each. The sites are maybe 1500 ft. apart, and one would get insanely attacked by JB.s most years (they’d fall on you like rain when you picked the fruit) while the other only suffered a scattering that required no intervention. If JB’s are consistently mobile, how do you explain that? I finally treated the attacked orchard with MS and for the last 2 years have not had any major problems, which may, of course, be a coincidence. The same year I treated that orchard I treated another with no appreciable improvement. However, I tend to take horticultural research with a grain of salt because results are never conclusive and only suggestive. In the realm of human medicine, where much more research is done and standards are higher (as far as being able to assert conclusions), different studies often reveal different results- presumably in horticulture many established by research truths would be brought into question if a greater amount of research was done. In the case of MS, maybe they’d find that in some situations it works well. Of course, when research, however scant, validates my only personal experience, I’m likely to fully embrace it with open arms. Certainty is such a nice luxury!