Japanese beetle control

I'm hoping someone can help me out with an urgent situation in zone 7A.  

For the past couple of weeks I have been noticing Japanese beetles all over a large patch of dogbane that is growing in my field.  This dogbane is growing back after my neighbor came and cut the field for hay a month ago.  However, this morning I noticed that the yearling plum tree sapling that I planted this spring (as part of a permaculture food forest that I'm trying to create) was being ravaged by Japanese beetles as well.  Almost every leaf was chewed up.  I already have 2 Japanese beetle traps hanging nearby because last year they were attacking my hibiscus flowers in droves!  It is obscene how many Japanese beetles are around right now.  Does anybody have a mitigation strategy?  I really don't want to start spraying the plum tree with chemicals

Maybe relocate the traps? Are they between the dogbane and your plants? Upwind? If they are already on your plants in numbers, it may be too late if that's the issue. They are very difficult to repel, even with modern insecticides, especially naturally.

Yeah Jordan, maybe I will relocate the traps in between the dogbane and the plum tree.  They're around 20 yards apart.

With the traps, you can put a big dent in the population, but you'll need a lot of traps spread out over a few acres. At one point, I had close to a dozen traps spread over five acres, and it did seem like there was some reduction in the beetle population. The little bags that come with the traps fill up quickly, so I'd suggest having the traps direct to larger containers.

Even with that many traps, the plum trees still got hit hard, so there definitely was a temptation to drench a or two tree in toxic gick to turn them into giant beetle killing traps.

Thanks for the post John.  I think I will be stopping on the way home for a few more traps.  I'll see if that works before using the toxic gick!  

Chickens got rid of the JBs in my garden. They ate so many of them in the grub stage, that I haven't seen an adult beetle around here in almost 2 years.

I used to know a guy whose chickens would eat the adult beetles, but it seems to vary by flock. Mine can't stand the adult ones. But, if you manage to get a flock that will eat them, you can redirect one of those traps so it drops the beetle into a dish of water. That slows them down enough for the chickens to grab them, but if there isn't a chicken around they'll eventually climb out on their own. That keeps the water dish from filling with dead beetle carcasses.

I need to get some chickens Ellendra, but I'm not quite there yet!  Thanks for the info.

I would cover the plum tree with something that the beetle cannot get into. Anything that would work, even an old sheet.  There may not be any leaves left though the tree will want to put new leaves out.

It is surprising to me that plants still can get sunlight even when covered with an old sheet.

Ugh, we have had problems with them the last two years on corn and blueberries. I'm trying beneficial nematodes this year. I realize it won't have an immediate effect but I'm trying to think longterm. I also use neem sprays which should deter feeding. Our ducks eat them but it's hard to measure the effect size there. I had a bucket on the porch that I had picked cherries in this weekend and hadn't rinsed. This morning there are probably 30+ japanese beetles in there. There's always hand picking or knocking them off the target tree into a soapy water bucket (this worked well with the blueberries). I don't use traps myself for fear of attracting more beetles. Best of luck.

Great tip Anne.  Yes, the leaves are almost gone and it happened so quick!

Noel, those are good ideas.  Yeah, I spent about an hour last night and this morning picking the beetles off of the dogbane and plum and into soapy water.  Hopefully when I get home tonight there will be noticeably less, but I'm not holding my breath!

I feel your pain! Our young plum (maybe 4 or 5 years old?) has been hit hard the past two years. They tried really hard to defoliate the poor little guy. This year, he is looking pretty lush and healthy again, but the Japanese beetles aren't quite out here. Probably soon. My plan is the soapy water bucket. I don't even "pick" them... I just hold the bucket under a branch and give a swift downward swat of the branch and they fall right in the water. I do find you have to do this every day, for the whole beetle season. I think I gave up too early last year. No giving up this year... may end up covering in netting if it all becomes too much.

plant 4 o'clocks. The humming birds and bees love them, but from what i have read and seen, they are toxic to Japanese beetles. They are also toxic to humans and dogs. My dogs haven't tried to eat the ones I have, and one of my dogs is part goat.

Heidi, since I posted this, I have been going out every evening and walking through the dogbane patch, plum, hibiscus tree (and now asparagus and elderberry) and putting them into a bucket of soapy water.  After 3 days even I have made a very noticeable dent in the population, so between that and my two traps I think it's working!  Persevere fellow Permies!

Thanks for that tip, Redd.  I read that somewhere as well.  Do you start yours from seed? I assume in 8a they are NOT perennial?

@josh
My 4 o'clocks are perennials.

They die back fully every winter (all 4 weeks LOL).  They produce seeds all season. The parent plants are growing from tubers, that get to be the size of softballs.

I am happy to send seeds if you send me a SASE. I am not sure how get you my address... purple moosages?

I know this isnt the most permies solution, but I have a cordless blower i run in reverse to chop them up. My chickens won't eat the mature ones, but they are definitely fewer.

That sounds like fun, Tj!  I have been diligent at picking them into a bucket of soapy water, and after 5-6 days there is a noticeable difference.  Permaculture solutions!

Redd Hudson wrote:@josh
My 4 o'clocks are perennials.

They die back fully every winter (all 4 weeks LOL).  They produce seeds all season. The parent plants are growing from tubers, that get to be the size of softballs.

I am happy to send seeds if you send me a SASE. I am not sure how get you my address... purple moosages?

Hey Redd, I just emailed you.

hi Josh, I got your email. I will send them end of the week.

Glad I found this thread. We never had problems with these pests until recently. They started last year decimating my raspberries. Didn't know what they were at first, and describing them to others didn't help. Finally identified the little buggers and now they're attacking my bean plants.

I'm definitely planting a bunch of JB repelling flowers! I read somewhere that marigolds are good, and I think something about geraniums (can't remember if the beetles like them or hate them).

Starting July 1st, we've been picking 100-200 JB per day with a peak of 300. After 6 weeks the numbers are down to about 50 per day. Our chickens don't like them, but our one remaining duck LOVES them. I collect into a water bottle that has had its top cut off and inverted into the bottle like a funnel. I knock the beetles into this "trap" and keep it swirled around as I go so they don't fly up and out of the hole.  The duck knows that swishing sound of beetles and is waiting in the coop at her water dish where I dump them into the water and she gobbles them up. She can eat about a quarter cup of bugs at one session without any of them getting out of the water. My husband and I each  make about 4 passes a day through the garden with the mid day hours being the highest numbers. At that time of day they are the most active and flighty and harder to catch but can sometimes be grabbed by hand in mid flight before landing. In our SE Minnesota garden they are most attracted to: grapes, raspberries, hazelnuts, aronia, common beans (especially black beans & pole beans), soy beans, amaranth, sorghum and corn. They don't appear to eat the corn and sorghum leaves but do sit on them, I think to attrack a mate? I often find them in corn tassels, sorghum and amaranth seed heads when they are pollinating so I suspect they are eating pollen? They don't seem attracted to the Kew Blue pole beans on the same trellis as the Early Riser pole beans and my theory is that the dark colored leaves camouflage their irridescent colors - I suspect that a visual clue might be an additional attractant to their pheremone scent? Also, they don't bother runner beans or cowpeas, even though they are interspersed with the common beans. I do see them sitting occasionally on the cowpea leaves, once again conspicuous like on the corn/sorghum leaves. I saw an interview with a southern gardener on PBS and his garden beans were really eaten up but his cowpeas looked pristine. Anyone else noticing this? On the runner beans I find them in the flowers, maybe after the pollen? So many questions to explore from my observations but too busy picking bugs to research ;>(. As for the wild plants in and around the garden the JB eat jewelweed, virginia creeper, nettles (mostly on the flower clusters - pollen?), and one plant of the hundred or so comfrey plants. It seems that there are "hot spots" that must become pheremone "wild traps" that they keep going to. As the season progresses, coupled pairs give way to clusters of 4-8 bugs on one leaf, really satisfying to scoop up a bunch at once. I've read that a number of song birds eat the grubs as do critters like moles and skunks but only a couple of species stood out as to eating adult bugs, starlings, robins, and cardinals, the later two I have spotted "working" in our garden but haven't gotten close enough to see what they're eating. We've only had them for about 4 years here and they're not yet widespread. Our neighbor, about 750' away, only has a few but she doesn't have the perennial crops or as many legumes as we have. I think that JB are part of our new "normal" and I shudder to think what our garden would look like if 4000-5000 bugs had been left to eat and reproduce.

Larisa, are you planning on planting some of those 4 0'clocks like Redd suggested?  I am going to try planting those all over the garden next year and can't wait to see the results!

I may try that, but our garden is quite large and the perennial crops are spread out over a large area so not sure how useful they would be. Seems like if they are toxic that the JB wouldn't be attracted to them but rather to their favorite crops. I forgot to mention sweet potatoes as a food crop in my prior post. It gets hit less often than the others. In my observations height is preferred to low-growing plants - tops of pole bean trellis versus bush plants. Maybe more of their wanting to be seen? If the sweet potatoes were on a trellis I suspect that they would take more of a hit. Other folks in our area mentioned that their apple trees were being defoliated and we're not seeing that here. Also another person said that they had very few JB but their neighbor's linden tree was covered. We have a small linden tree planted and it's fine, so not sure if plant species is as important as pheremone draw to a particular plant/planting. For instance, on pole beans it's the same leaves that get gathered on day after day, until there's not much leaf left from all the munching. When the beans go into dry down stage, the JB leave them alone and gather back on the perennials. In another observation, we have a separate older orchard fenced with 4 chickens and our 1 duck. In there are 40 older and very tall (10'+) hazelnut bushes. You can see there is some damage but not too bad. I'm wondering if the JB go down from the bush tops at night to "sleep" and if so, perhaps the poultry are getting them? They certainly are always in a hurry to get out in the morning, forgoing their feed. I don't find JB on top of plants first thing in the morning other than the occasional slow-moving one, so thinking that they must go somewhere? I have more questions than answers it seems.

I had big issues with Japanese beetles in our old place last year. Neem oil did and didn’t help- If I sprayed something they were attacking the next day they’d all be congregated on a new type of plant. Corn -> sweet potatoes -> squash and so on I was just chasing them through the garden. Heidi’s method of knocking them into a bucket was the most effective thing I did. Also I noticed they preferred some of my lawn weeks to vegetables so I stopped mowing a few patches and that seemed to work as a trap crop- specifically dock and some sort of mystery vining weed growing along the fences.


Japanese beetle grubs overwinter under turf, so if they are really an issue year on year it may be beneficial to reduce the amount of lawn. However if you have close neighbors it won’t do anything, as the beetles from their years will be in yours very quickly. Michigan state university’s site claims it can take 5-10 years for natural control like parasitic wasps to kick in within and infested area. I still think If these lil jerks are a big problems it’s be worth giving nature a nudge and trying to attract more parasitic wasps. Fortunately moving seemed to be the ticket for me, I only saw 1 beetle on our property this year.