Thursday, July 28, 2011

this is your garden on japanese beetles. minnesota 2011

on our 'black ice' plum tree planted this spring
More accurate is to say 'japanese beetles on your garden'.  I just like the 80's reference.

The infestation has gotten worse since I wrote the last column about japanese beetles.  I've picked off a few hundred in our yard thus far.  At first I tried picking them off, then stepping on them, but some flew away.  So now I crush them a bit between my thumb and forefinger, then step on them. That works.

It seems a bit cruel- but look at what they're doing to my garden.  To the fruit trees as well as my roses. 

To be honest, they are beautiful bugs.  If there were only a few, I wouldn't mind.  I like to see a diversity of critters in the garden, and I can and do tolerate a few holes in leaves and a few missing fruits and veggies here and there.

But these are overwhelming.  They're all over this year.  At least in St. Paul and Minneapolis.  Our community garden has the worst infestation I've ever seen.  There are two traps (see bottom photo) in the garden now, and they both seem to fill most of the way up each day- that would probably total over 10,000 trapped per day- to estimate very roughly.  We filled a 5-gallon pail well over half full with beetles and soapy water in less than a week.

this one seemed to enjoy posing for the photo

typical japanese beetle damage

on the 'winnipeg parks' roses

and a clusterf--- going on in the 'morden blush'!

They really love the roses.  I found 4 or 5 in the above 'Morden Blush' rose alone.  The soybeans in our neighbor's plot at the community garden has them pretty bad as well.  They hand pick pretty often, but they're still noticeable. 

I'm looking into long-term options now.  I'm thinking that I'll treat the yard with Milky Spore and a beneficial nematode once it cools down a bit in late August.  I'm trying to find a place that sells the right nematode.  Egg Plant had the Milky Spore, but not the right nematode.  I may have to mail order it, even though I don't like to mail order something that's supposed to be delivered alive.

Taking a closer look at the non-organic options recommended by the U of Mn Extension office (no, I'm not considering going that route) I noticed that they are recommending imidacloprid for treatment of adult japanese beetles.  I've noticed some other sources recommending the same.  

I'm sure that it kills them off.  But the cure may end up being worse than the disease.  As I wrote about in this article in April, imidacloprid has been accused by credible sources as being responsible for mass honeybee die-off.  Whether it and other nicotinoid insecticides are really the smoking gun in colony collapse disorder is difficult to say.  I'm a landscape architect, not an entomologist.  But I would hope that anyone considering using this chemical to control what is a temporary problem consider the long-term effect of also killing our best source of free garden help- the pollinators- the ones that make fruit possible.

some of the non-toxic treatment options
At the moment, at the community garden, we're using a 5-gallon pail filled with soapy water (both dish soap and some car wash are used--both are effective--they're just what we happened to have in the basement).  I put it below the trap to catch any beetles that are attracted to the pheremones, but lose their footing on the outside of the plastic trap.

Long term, we'll have to find the Milky Spore and nematodes.  Our garden will survive and we'll take these buggers down while they're in the ground.  That's all there is to it.


  1. Jeff, thanks for the heads up. I better go out and check what's going on out there! I did quite a bit of garden work earlier in the week, and I think I spotted two of these beetles--and managed to kill one. I have not noticed leaf damage yet.--Jodi

  2. I don't know if you have chickens, but I set up a trap with a long plastic tube (from an old lawnmower) instead of a bag.

    Then I run the tube into a pan of water with no soap. The beetles slide into the water, where the chickens gobble them up.

  3. Hi Jodi,
    Take a look at any fruit trees or roses you have. I can almost guarantee you'll find some. At least if you're anywhere near the Twin Cities. I've found that hand picking really does keep them down. I've been picking them every day almost and my plants are doing way better than similar ones I've seen in nearby yards.

    Wagelaborer- thanks for the tip! If I had chickens I'd definitely try this. I love it!
    Actually, I brought up the idea of chickens a week or two ago to my wife, Gita. I thought she'd just say 'no' right away, but she liked the idea. She even started talking me into the idea- for the benefit of the kids of course. So maybe next spring we'll get a couple of little chicks. I hear that chickens find japanese beetles to be delicious.

  4. Darn Japanese Beetles! They ate all my roses.But they look beautiful just like my favorite lady bugs.