Thursday, July 21, 2016

Attacking Japanese Beetles -- Know Your Enemy

Author's note: If you haven't read my last post: "Attacking Japanese Beetles -- Organically", please take a look at it.  You will learn more from this post if you read my last one first:

JBs on Earth Song

To get to know the JB enemy, let's consider again where JBs originate.  The adult beetles mate in the process of feeding on their favorite foods (like roses, many trees and other flowers like zinnias) and you can see this happening if you observe them clustering.  The female JB then finds a lush bit of turf and deposits her eggs.  The eggs hatch as grubs and feed on the grass roots.  If enough JB grubs populate your lawn, you will develop areas of dead turf, which, when dug up, will have one-inch, white, JB grubs clustered in the roots.  That whole area of your lawn will die unless you apply grub control in the fall or early spring.  This is one of the things that golf course managers have learned and why they have been using huge amounts of imidacloprid, as the most effective grub control, over the last several years here in Minnesota.  I had this problem myself, several years ago, and applied granular imidacloprid to save my lawn.  You can bet that this is part of the reason that we have seen such an upswing in bee colony collapse disorder, which has been directly linked to imidacloprid.  One extreme example of this is Orem City, Utah, which applied imidacloprid across all neighborhoods of the city, several years ago, when JBs began to affect the floraculture and nursery industries. They even went so far as to warn homeowners not to eat any of the produce of their fruit trees, because of the systemic nature of imidacloprid. It worked, but I can't even contemplate the extent of the damage to honey bees and other beneficial insects, like lady beetles, in Utah, as the result of this extreme measure.  Here's the Utah story:

I also want to point out that as soon as we began to see JBs in the Twin Cities, I made the rather sizable investment in Milky Spore, with a special tubular applicator and all, and went all over my lawn and portions of my neighbors' lawns laboriously applying patches of it, exactly as specified (and I breathed-in a lot of it, as well).  I watched, hopefully, for the next few years to see what the milky spore infection would do to the JB population on my roses and I can say with certainty that it did virtually nothing to significantly reduce the population of beetles in my gardens! Oh, I'm sure that Milky Spore and a subsequent, equally expensive, application of nematodes knocked off a bunch of JB grubs in my lawn over the next few years, and they still may be doing so, but that's not where the great majority of JBs landing in my gardens are originating.

Please see quotes from the University of Minnesota about the ineffectiveness of Milky Spore here:

Fact: JBs travel amazing distances, from where they pupate, to find the plant foods they relish (like your roses).  There is evidence that they may fly as much as five miles to reach your plants, so unless all the turf within a five-mile radius of your garden is treated with Milky Spore or imidacloprid (like in Utah!) there is no way that what you alone do to your lawn will stop JBs from invading your gardens. Milky Spore and imidacloprid can protect your lawn from dying, but they can't stop the vast majority of JBs from flying your way each summer.  Save your money and concentrate on killing the JBs as they arrive, before they can lay eggs in your lawn.  As I point out in my earlier blog posts, pyrethroid insecticides, like Demand CS, work well, but they also kill beneficial insects such as lady beetles and pollinators. That is why I advocate the organic approach of manually drowning JBs. Either way you decide to go, it's far more important to concentrate on attacking and killing JBs than it is to try and prevent them from hatching on your property.

Fact: If you haven't already figured this out, JBs are amazingly canny critters. To effectively attack them, it's useful to observe what they do as they approach your garden.  When you have as many as I do, it's interesting to observe their behavior (just before drowning them!). When a JB arrives in one of my rose beds it hovers around the bed, like a helicopter, looking for a suitable place to land. Almost always, it will land on a flower or leaf that has one or more JBs already on it, or on a flower or leaf that has been previously chewed by other JBs. So, obviously, the JBs arriving in my garden, from some distance, perhaps miles away, are attracted to the scent of other JBs, presumably by the female sexual pheromone, which is all kind of amazing to me. So, it's important to get rid of tainted leafs and flowers, whenever possible.  I know how hard it is to pluck a brand new bud that has two JBs imbedded in it, but it's important to do that in order not to let it attract incoming beetles (I did it just a few minutes ago and it is painful).  Interesingly, when they can't find an old leaf or flower to land on, they seem momentarily confused and can be easily picked off. Also, believe it or not, while they are hovering around looking for a place to land, I have been quite successful in grabbing them in mid-air!  That actually makes the whole exercise kind of fun once in a while.

The good news is that JB season should soon be over.  They started early this year (June 19th) so they should soon be finished. Better days ahead.

Jack Falker
July 21, 2016


  1. Thank you for continuing to post about JB's, and thank you for mentioning me in your previous post. You and Paul Zimmerman were the only two people to give me any realistic and healthy advice. Question: Where do you toss your bug water? I thought it might attract more, so I have been trying to carry it off away from the garden. Does it matter? I have had a bit of a mystery though. Something is eating the beetles out of the bucket. I am 100% sure the beetles are dead. Depending on how many beetles are in the bucket, it takes about 24-48 hours for them to disappear. It has happened several times. Someone suggested a crow. Whatever it is, is leaves no sign behind that it was there...only the missing beetles. Any idea what likes to eat Japanese Beetles? I should mention, my beetle population hasn't slowed at all and it's now 8/3.

    1. Hi Michelle... Sorry it took me so long to respond. I usually dispose of the drowned JBs down the toilet into our public sewer system. If you are on a septic system out in the country I would check with your service person to find out if it's ok to put dead insects in there. Otherwise, I would probably pour them into a strainer to get rid of the water and just put them in a plastic bag to dispose of in your garbage collection. I don't think it would be a good idea to put them in a compost collection, if you have one, because it seems like the fertilized eggs might survive to hatch in a mulch pile somewhere. So the toilet or the garbage seems to be the same way.

      Ha... I can't imagine what is eating your beetles but your idea of a big bird like a crow makes sense. Do you have wild turkeys? Somone told me they like to eat JBs. Birds in general seem to feed on them. In my case, goldfinches seem to go after them; I just wish I had more birds to help me out :) .

      My beetle attack has finally started to slow down. I haven't been out today but they have definitely been fewer in the last few days. They started June 19th, so we're almost at two months now. Having said that, I have seen them last till labor day. I think Paul said they lasted about a month in SC.

      I give you a lot of credit for trying to do this organically. When you see bees and predatory wasps pollinating and feeding in your garden, you can take great pleasure in knowing you aren't harming them.

      Best regards,

  2. It's looking amazing to read your blog as it contains informative points that are helpful in order to put control and protect the flowers in garden from the enemy insects and thanks for updating about JBs and continue posting such informative blogs.