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Japanese beetle population boom

Cluster of Japanese beetlesWe always have some Japanese beetles, but they usually stay on the cherry tree, raspberries, and grapes.  This year, I have to walk through the whole garden picking bugs because the invasive pests are chowing down on everything from Swiss chard and corn to breadseed poppies.

I can't quite figure out what tipped the balance to create this shift.  Perhaps Mark's been keeping the lawn mowed too well so the larval stage is happier, or maybe ripping out those French grapes deleted my trap crop and spread the insects far and wide?  Another option would be this year's rainy weather since drought can kill Japanese beetles in the grub stage.

Whatever the cause, I've been handpicking like crazy and making no dent.  I fed a full cup of Japanese beetles to the chickens on Thursday and immediately saw more insects that I'd missed.  I'd be curious to hear if you're overrun with more Japanese Nymph wheel bugbeetles than usual this year or if the plague is confined to my garden.

The good news is that our predatory insects might take up the slack before long.  I've seen hundreds of small praying mantises this year, so hopefully some of them will rise to the occasion.  Meanwhile, I started noticing assassin bugs hanging out where the Japanese beetles land and even saw one Japanese beetle husk --- the hard carapace remained but nothing inside.

I think this guy is, more specifically, a nymph Wheel Bug (Arilus cristatus), but all assasin bugs work pretty much alike.  They use those long mouthparts (see the yellow bit curving down below the insect's face?) to stab insects and inject a chemical that liquifies the prey's internal organs.  Then the bugs simply suck their dinner dry.  Take that, you Japanese beetles!

Learn to keep bugs at bay

Our chicken waterer keeps the flock entertained when I'm not tossing in weeds, worms, or beetles.



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I suspect that it might be the mowing...but I will have to see how I do this year.

I tend to let our fields grow up a fair bit, and while I have seen many of the beetles in past years, they have stayed to the plants there rather than go after my garden. I THINK they were mostly on the milkweed last year.

All that said, I am about 2 weeks or so behind you, (I am on a mountain in Berkeley Springs, WV), so we will see what issues I have in a bit. (grins)

Comment by Geoffrey Wendel Fri Jun 24 09:05:31 2011
You might try looking into 'Milky Spore' to interrupt their lifecycle. It can take several years but is well worth it. We lost a dry bean crop to them last year. They are just beginning to come out, here in eastern Missouri but we just got done with a 13 year periodical cicada hatch as well! Good luck!
Comment by Pat Fri Jun 24 13:22:49 2011
I don't know about japanese beatles but many other insects have multi-year cycles. cycadas= 13. box elder bugs =7. gypsy moth = ?. is it possible that these beatles also happen to have cycles of bad and good years? Often times what happens is that they breed more and more each year until they reach some threshhold at which high numbers causes a population crash due to predators and disease and the multiyear cycle starts over again. sometimes insects are particularly bad if the previous year was good for them wet/dry/hot whatever or if the winter happened to be particularly kind (not killing off as many eggs through warm and cold cycles).
Comment by rebecca Fri Jun 24 14:18:22 2011

Geoffrey --- I hope it's not the mowing --- it sure is nice to be able to walk down our garden aisles... :-)

Pat --- I've considered Milky Spore, but our beetles have never been bad enough to make it worthwhile. If this is the trend of the future, though, we're going to have to treat next chance we get (which I understand would be in the spring.)

Rebecca --- Intriguing idea. I'd love it if that were the case! Maybe if we're lucky, next year will be a bad year....

Comment by anna Fri Jun 24 18:59:12 2011
Well at least there is alot of protein for the chickens to eat. Thats something.
Comment by Lisa Sun Jun 26 00:10:53 2011
Our flock agrees with you completely. "We don't see any problem with the Japanese beetle infestation this year!" they assert. :-)
Comment by anna Sun Jun 26 19:30:03 2011

I haven't seen any Japanese Beetles this year but then again they've never been a problem for me yet. I am currently dealing with some cabbage worm moths that I need to buy a butterfly net for.

I hope the assassin bugs and other good guys help you out soon!

Comment by diggitydog Tue Jul 5 20:30:30 2011
I'm convinced it's due to the rainy spring/summer. 2 years ago I had them BAD, than last year, one here and there..nothing really. This year they are back and everywhere! Last spring/summer was very dry. I think it has everything to do with how much rain there is during the season. I wish I knew a quick, easy way to rid myself of these buggers, nothing seems to deter them and never imagined they'd eat marigolds, zinnia and basil. My Zinnia seems to be their favorite with basil in close second.
Comment by Holly Tue Jul 5 22:09:07 2011

Diggitydog --- I'll keep my fingers crossed that they stay away from you. We do pretty well with cabbage moths just by not having crucifers in the garden during their peak flying time. I guess I should really be counting all of the bugs who don't cause us much trouble, not the one who does.

Holly --- You're probably right about the rain. Our summer's been normally rainy lately (which means a few storms a week), but it was seriously wet this spring. Hopefully you'll have a better year next year.

Comment by anna Wed Jul 6 13:14:31 2011
We live in the suburbs of Raleigh, NC. We have lived here for over six years and every year we have had large amounts of Japanese beetles. For some reason, this year we have almost none. Maybe they all moved to your area :)
Comment by Anonymous Mon Jul 11 10:48:37 2011
Why didn't you keep them?!
Comment by anna Mon Jul 11 13:08:06 2011
I hope everyone is correct about the wet spring and that wet springs do not become a common occurance in east central Wisconsin. I have been plagued with these nasty bugs for 3 years now, but this year was by far the worst. Their favorite food is my beautiful Mount Saint Helens plum tree and a close second is my pole beans. From July through early Septmber, I have been picking them off my tree and plants twice a day and dropping them into a bowl of warm soap water. The bowl is approximately 6 inches in diameter and at their peak, the surface of the bowl would be covered with 3 layers of the pests. Although the milky spores sound like a good solution to bug control, I wonder if this in turn is destroying other beneficial organisms in the soil.
Comment by Kathy Sun Sep 18 15:38:44 2011
I know what you mean --- I finally stopped handpicking them around the end of September. The plants they loved were eaten to nubbins, and they'd pretty much stopped going anywhere else. Hopefully next year will be better....
Comment by anna Sun Sep 18 20:18:17 2011

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