Hi y'all, This spring and summer I had a particularly hard time with Japanese beetles. As an organic gardener, I just removed, by hand, all bugs I saw. A little damage I expect and can deal with - but I thought this year's defoliation was excessive! As far as I know, the life cycle of these bad boys includes a larval stage in soil. My question is then, would beneficial nematodes be a way to fight my beetle problem? If so, when is the correct time to apply the nematodes? I am experienced with the use of beneficial nematodes for lawn care use and understand how they work in the soil. I believe in their benefit wholeheartedly. All my trees are in pots however, so I don't know if that is an environment in which the good guys could thrive, or do any of their good work. Beneficial nematodes are not exactly cheap, so I want to make sure my inclination to apply them to potted maples is a good one. Any thoughts/experience? Another question... I know that nematodes don't harm earthworms, but are they contra-indicated when trying to encourage beneficial bacteria in my containers? Nasty soil-borne diseases (that may or may not be thwarted by mycorrhizae - that's a different thread) are much harder to fight than silly, shiny, beetles, so I definitely don't want to discourage any helpful microorganisms in my pots. I don't know how, or even if, mycorrhizae and beneficial nematodes interact, so it may seem like a dumb question, but I love JMs enough to look stupid in front of all you experts in this forum. :) I'd love to hear your thoughts. Thank you for your help!
Spookie, You have a problem many of us deal with, but it isn't an easy one to control. Yes, nematodes are beneficial. However, the most beneficial organic treatment is Milky Spore Disease. This attacks the grubs and kills them in the soil, much as the nematodes would, but unlike the nematodes Milky Spore can last up to 20 years! Milky Spore will also attack other beetle grubs in the soil. The best time to apply Milky Spore is RIGHT NOW, in the early fall, and in the early spring. I would highly recommend two applications (fall and spring). The Japanese Beetle grubs feed exclusively on grass roots. After the eggs hatch in early Sept, the young grubs migrate to shallow soil and feed on grass roots until the soil starts getting cold. Then they migrate deeper for the winter. In early spring they migrate to shallow soil again for a final round of feeding on the fresh new roots. Then they pupate and hatch out as adults in late June. So, if you apply the Milky Spore during the two periods when the grugs are near the surface, you have the best chance of infection. The younger the grub, the more susceptible they are to Milky Spore. After killing a grub, millions of Milky SPore are released into the soil where they can lie in wait for up to 20 years or a new host. They are completely non-toxic to humans, plants, pets, and other insects. The other thing to note is that the grubs will NOT be a problem in your JM pots. Like I said, they feed only on grass roots. Now, as exciting as this all is, there is one draw back to ANY Japanese Beetle eradication scheme - scope. You may treat your own yard with nematodes or Milky Spore, but your NEIGHBORS who did not will still harbor untold thousands of the little beasts! So even the best treatment is limited by scope. The most effective solution would be for you to convince your neighbors to also apply Milky Spore. If you can get most of the surrounding homes to join in the effort, it can have a noticeable effect. One note of caution - DO NOT use the scent traps popular at garden centers. Japanese Beetles can smell them and fly to them up to 3 miles away, so all you're doing is ringing the dinner bell for thousands of beetles to come to your yard and chow down! These traps are only effective if a large number of homes all use them at the same time. Again, the scope thing. Now, if you're like me, in the country with almost no one around, any of these treatments may be effective. I used traps last year and had almost no beetles this year. But I only have a small patch of grass on my 22 acres! This spring I'm getting the Milky Spore treatment, which should bring me long lasting relief and no messy traps. I would recommend buying Milky Spore directly from the manufacturer, as garden centers may have old stocks which may have been stored improperly. Here's the link: http://www.milkyspore.com/milkyspore.htm Take care!
FANTASTIC INFO K4! Thank you. I was not aware that Japanese beetle grubs would NOT be in my pots - only in the grass! Good to know. Its great that there is a non toxic treatment that is so effective. Hmmm. Your experience with the traps is helpful too. I had thought to buy some next summer as the beetles started appearing, but now know that is not such a great idea! I am not entirely sure what to do however, For neighbors I have a well-intentioned but compulsive sprayer of landscape poisions on one side (he's in the biz) and a master gardener with a shed full of antique toxins on the other. Unfortunately, this makes me the organic oasis for all the bugs! I am not sure Milky Spore will save me. Its worth a try. Are there birds that eat the little beetle buggers? Maybe I can attract those...
A few bird species will eat Japanese Beetles, but its really not something they're going to go after big time. Robins, Blue Jays are all I've ever heard of. They're a foreign bug, and the wildlife hasn't really developed a taste for them yet. I would try the Milky Spore anyway, and I would ask all the neighbors to try it as well. The 20 year life span of the treatment should be attractive to most of them with a brain... :-0
I ditto the thanks about the Milky Spore. I went directly to the site and noticed it was a powder. Does it only come in powder and how difficult is it to put on? I noticed there is a spray device for sale, too? Would you only put it on the grass, or on entire garden area? Thanks for this great info. Kay Dye P.S. I heard that if you take the beetles off by hand, you need to drop them in soapy water or alcohol, not smash them because they give off an odor that attracts others. Anyone else heard this?
Hi Kayde, Milky Spore comes as a powder because it needs to be kept cool before application (remember, in nature this stuff lives undergound, where its cooler). Once it becomes "activated" by becoming wet, it will need to be in contact with soil so it can move down into the layers where the grass roots are. In general, powders are also easier to apply at controlled rates. The application of Milky Spore is usually done by putting a couple of teaspoons of powder at four foot intervals in a grid pattern, then watering it in. The soil needs to be kept moist for several weeks, so watering is essential if your natural rainfall doesn't do the job. There is an application tube you can get that releases just the right amount powder with the push of a lever. They also make a granulated form that can be spread on your lawn by a mechanical spreader - the ones you would use to spread fertilizer and such. These granules are coated with the Milky Spore powder and dissolve into the soil when wet. Either application method is effective, but you must do it at the right times of year (early fall and early spring) to catch the beetle grubs near the surface of the soil so they can become infected with Milky Spore. And yes, if you pick beetles off by hand you should put them in a bucket of soapy water. Dead beetles should be put in trash bags and hauled away. Crushing the beetles or beetle carcases can release chemicals that attract more beetles. Females release a pheremone that attracts male beetles, and the beetles also mark the leaves they've been feeding on with a special "come and get it" scent! So it may also be wise to remove any heavily damaged leaves, as this scent will remain on them for a long time and continue to attract more beetles.
