Japanese beetles on blackberries

tworivers1July 2, 2008

I've been noticing Japanese beetles on my new blackberry plants (first year plants so no berries yet) and am wondering how big a problem they can become. At the moment I am just knocking them off and stepping on them as I normally only see four or five at a time. I'm hesitating to use the Sevin insecticide because of the fact you are not supposed to pick berries until seven days after you apply the insecticide and I'm not too comfortable with that. Any help will be greatly appreciated.


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Since your blackberry plants are first year, and won't blossom or set fruit anyway, I don't understand the reluctance to use Sevin or any other insecticide. Sevin is a non-persistent, contact insecticide that is very effective at knockdown of Japanese beetles. If beetles persist after your plants grow up and begin to produce, you can still use Sevin early, then stop after the plants begin to set fruit.

If you want a long-range, "organic" solution to JB's, apply milky spore around your yard, and as far into your neighbor's yards as they will allow you to go. I have applied it only twice here in 30 years; once in the late 70's, and again 3 years ago. I have zero JB's and many attractive plants and trees. Since the milky spore must find a few larvae to reproduce itself and remain effective in your soil, it eventually kills all the larvae and literally works itself out of a job.

That's when it's time to renew if the beetles return. Miky spore is not cheap, but worth every penny.

Don Yellman, Great Falls, VA

    Bookmark   July 2, 2008 at 2:00PM
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That makes sense. The only other question is if the Sevin will cause them to move to my tomato plants or new raspberries and strawberries.

I believe I will look at the milky spore for a long term solution because I really don't want to keep applying that much insecticide to everything.

Thanks a lot.

    Bookmark   July 2, 2008 at 7:04PM
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Any JB's hit with a spray of Sevin will be moving in only one direction, and that is straight down to the ground. Sevin has great knockdown power for JB's, but, unfortunately, little residual effect. So it's best to wait for a buildup on their favorite plants, then hit them when there are large numbers present.

JB's do like raspberries, but I have never seen them on strawberries or tomatoes.

My son has a purple leaf decorative plum that was severely infested 3 years ago. I gave it a thorough spraying with Sevin, and it literally rained beetles for the next 10 minutes. I subsequently treated his property -- 3 acres -- with only one 44 ounce can of milky spore, and he has not had beetles since. This was way below the recommended application rate, but that one can of pure spore was apparently enough to infect the numerous grubs in his soil and he now has total control. I spread the spore very thinly with the tube applicator on about a 10 foot grid. It took me several hours to walk his property and make the application.

Milky spore is also sold in a mix intended for application by broadcast spreaders, but this product is quite low in the percentage of pure spore, and ends up being considerably more expensive for what you get. It is, however, easier to apply.

Don Yellman, Great Falls, VA

    Bookmark   July 3, 2008 at 12:42AM
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seven will kill your earth worms also. go to lowes and buy japanese beetle traps. They work wonderful. I use them and caught about 100 in one day.

    Bookmark   July 3, 2008 at 11:08AM
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glenn_russell(6b RI)

The problem with the traps is that they often bring more beetles to the area... so they're kind of a mixed blessing.

    Bookmark   July 3, 2008 at 12:29PM
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I have never observed that Sevin or any other insecticide I spray on my trees or plants affects earthworms.

If you want a lot of earthworms, provide the right soil conditions for them -- deeply mulched beds with organic mulches, like stable manure. That is what I do, and the earthworms respond by the thousands. Mulch also insulates the soil against heat, which drives the earthworms down and stops their propagation.

I think Japanese beetle traps are expensive and worse than a waste of time. You can keep filling traps all summer, and the beetles will just keep coming in. What a stinky mess. Save your money.

Don Yellman, Great Falls, VA

    Bookmark   July 3, 2008 at 2:01PM
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I would avoid the traps. You'll just attract your neighbor's beetles. 2 summers ago I setup 2 traps and I would get a full bag daily...thousands and thousands of beetles over the summer. Ones that didn't make it into the trap then end up in your yard laying eggs for the next year.

We've done Milky Spore 3 times in our yard in the past 2 years and we still get beetles but their numbers are less. I plant to keep it up...I've used the spreader kind.

I hand pick them into a jar of soapy water now from everything they like. I have a new sweet cherry tree that they absolutely adore. I've been trying Neem Oil spray and it's helped a bit but is not a magic cure.

    Bookmark   July 4, 2008 at 5:27PM
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I'm still only seeing 5 or 6 every time I go out to check but they also seem to like my wife's zinnias and I've also found a couple on my tomato plants. I just bought the Sevin powder and will put that on my blackberries and when I get a chance I will put out the milky spore in the coming week/

    Bookmark   July 5, 2008 at 12:39PM
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Does anyone know if milky spore will kill green June Bugs too? They are eating my nectarines. Forget the soapy water in a bucket method. They are too fast, and trying to get the bucket near them usually results in knocking a bunch of nectarines off the tree. However June Bugs are great fliers, so don't know if killing the bugs on my property would do any good, everybody within a mile would probably have to use it too.

    Bookmark   July 5, 2008 at 1:14PM
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ladyslppr(z6 PA)

I am not sure why you are worried about which insecticide to use when you are only seeing a few Japanese Beetles at a time. Picking them off the plants and crushing them should work fine for 5 or 6 at a time. I would hold off on the Sevin until you start to see significant damage to your plants. Spraying the plants for a handful of beetles seems like an unnecessary use of insecticide to me.

    Bookmark   July 5, 2008 at 9:20PM
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Milky spore kills the grubs in the ground and needs to build up over several seasons to be effective from what I've read. It won't do anything for green beetles this season.

I wish I had 5-6 on my plants. I've collected several hundred using the soapy water technique in my backyard the past few days. They are all over by love a 15 foot Kwanzan cherry (half dead from the past few seasons attacks) and a new sweet cherry I just planted. (now bird-netted it a weak attempt to save it)

The one thing to try to do is keep their numbers down early in the season so they don't spread the pheromones around one plant or area. Other beetles are attracted to the smell and it can snowball so you have hundreds of beetles on one large plant. We had a 8' weeping cherry we removed last summer because it had a huge infestation on it that basically killed it.

    Bookmark   July 6, 2008 at 4:51PM
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