Why not mention milky spore for long-term japanese beetle control?

Asked August 21, 2018, 11:35 AM EDT

I see no mention of milky spore at either https://extension.umd.edu/hgic/japanese-beetles or https://extension.umd.edu/sites/extension.umd.edu/files/_docs/programs/hgic/HGIC_Pubs/Insect_pests/HG78%20Japanese%20Beetle_2018.pdf . Milky spore has been recommended by others in the past. "The USDA has approved milky spore for use on the beetle grubs. It states that milky spore is not considered harmful to humans, birds, dogs, and other animals." . https://www.arbico-organics.com/product/milky-spore-granular-bacillus-popillae/japanese-beetles-control has "Treat with a combination of Milky Spore and NemaSeek Beneficial Nematodes in spring. This combination is the most effective treatment for prolonged control of the grubs".

Montgomery County Maryland

3 Responses

Our research showed us years ago that the milky spore available for purchase was not as effective as the original population had been. Because of that, and the high cost, we do not recommend it to homeowners.

There are effective and very low toxicity materials on the market now for lawn grub control. Grub problems in turf are quite rare. (A few grubs in a lawn are not damaging and actually good, because it keeps their predators around.) Grub control is usually not a solution to lawn problems.


Thanks for your quick response.
I accept (but not totally) that milky spore is no longer recommend it, but I have further question(s) / comment(s).
1. I am not sure of the meaning of "population" in your "not as effective as the original population had been" . I'll guess you mean "batch of originally produced product".
2. You mention that "Grub control is usually not a solution to lawn problems." But remember that I want to control the japanese beetles via destroying their grubs rather than merely trying to improve the lawn. Here is my situation. I have more than 20 chinese elm trees that I've tried to trim to be merely a huge hedge along a 70 ft. line. The last few years, thousands of j beetles feed and mate on them each year; a few of them feed on some nearby pears, blackberries, and a crepe myrtle. Baited traps are imperfect. I manually caught (and eventually killed and buried deep) hundreds of the beetles daily. I assume the fertilized female ones I don't catch fall from the trees to the ground to lay their eggs. If I could have milky spore kill a very large percentage of their grubs, I would be doing myself and neigborhood a long-term favor. I have used milky spore in and around that area sporadically (maybe 3 times) over the last few (maybe 10) years. I realize that is not the recommended dosage. I bring this up partly to see if this is a reasonable neighborhood solution - use a decoy crop (such as chinese elm trees) to attract the j beetles, whose next generation would be killed by milky spore or your currently recommended j beetle grub killer.
3. Probably due to some other reason, I've only seen two or so j beetles this year! Some of that is likely due to changes in my attentiveness / habits. I don't know if some neighborhood activity is the cause of the drastic decline. Even if my milky spore application killed many larvae, surely j. beetles that hatched from neighboring areas would find their way to my trees that the j. beetles have loved so much.
4. I live in Clarksburg, so maybe the area's ruralness and development practices have caused the huge population (up until this year).

In many areas Japanese Beetle populations were not high this year. The populations can vary greatly from year to year based primarily on how dry the ground is when they seek to lay eggs the year before.
The original research results of using milky spore were not able to be replicated by others. That poor efficacy and high cost are why we don't recommend it.
However, the newer Grub-Ex products are effective with reduced toxicity than previously.
We don't recommend traps either. They tend to bring more jb to your yard than you would have otherwise.

Your 'trap crop' idea may not work depending on the grass varieties growing. The recommended lawn grass in Maryland is turf-type tall fescue, and those lawns aren't terribly bothered by grubs, and likely used less often for reproduction. You might aim your control around the favored feeding sites.

Here is our page on grubs: http://extension.umd.edu/hgic/grubs-lawns and here is our page on japanese beetles: http://extension.umd.edu/hgic/japanese-beetles