Scale on japanese maples

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Scale on japanese maples

Post  Cole on Thu Apr 02, 2009 4:27 pm

I have a developing scale problem on several varieties of japanese maples. A local nursery has suggested using a systemic (Bayer Advanced Tree Protect & Feed, active ingredient...Imidacloprid). Is this a safe remedy? If so, what dosage? Is this better than simply using insectcidal soap?

The trees are grown from cuttings, 20 years old, 1"-2" trunk, 2'-3' tall, Sacramento Valley at 700 ft elevation.

Thanks, Mike

Cole
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Re: Scale on japanese maples

Post  Kev Bailey on Thu Apr 02, 2009 5:02 pm

I would advise strongly against using that chemical. It is implicated in the collapse of bee populations and that is something that everyone shopuld be concerned about. Take a look at this "Imidacloprid effects on bee population"

Insecticidal soap is effective, especially if you mix some rubbing alcohol in to help break down the waxy coating of the scale.

However, scale rarely kills unless left alone to proliferate. If you have a wild bird population that can be encouraged to spend time near the trees, they will often clear the problem completely, once they discover an easy food source. If that doesn't work, try wearing gardening gloves and wiping/squashing them and dropping them into a bucket of soapy water will get rid of most of the adults. Then blast the smaller ones with a strong hose to wash them off.

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Re: Scale on japanese maples

Post  Nina on Fri Apr 03, 2009 12:40 am

At the last meeting I was at, the speaker showed evidence that Imidacloprid had no correlation with bee collapse, and my entomologist friends agree. However, Imidacloprid is an important insecticide (safe and effective at low doses) and should be used at part of an integrated pest management program to make sure insects don't become resistant to it. For something as easy to control as scale on bonsai, I wouldn't use this. I'd use a piece of paper towel dipped in soapy water to rub off as much as I could by hand, I'd rinse the tree, and then I'd apply a pyrethrin insecticide. Or what Kev said.

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Re: Scale on japanese maples

Post  JimLewis on Fri Apr 03, 2009 1:34 pm

I totally agree with Nina. I use a pyrethrin insecticide for what few bug problems I have. It kills on contact. It has virtually no residual effect.

Note: I have VERY few bug problems now. We have a "heard" of wild chickens on our place -- they wandered off from a neighbor's coop. In addition to a wonderful 3 a.m. (and periodically thereafter) alarm clock, and a seemingly endless supply of fertile eggs, we have almost no bugs. Alas, though, the butterfly population (except for those that have ugly tasting larvae) is down.

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Re: Scale on japanese maples

Post  John Quinn on Sat Apr 04, 2009 3:05 am

I thought I recalled reading 'somewhere' that pyrethrins could be phytotoxic to some Japanese maples. Nina,you apparently feel they are safe!

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Re: Scale on japanese maples

Post  Nina on Sat Apr 04, 2009 4:44 pm

I'd test the pyrethrins first, then use.

The key is to understand the product, the plant, the pest, and the timing. My figs hate insecticidal soaps, but it controls their scale problems, so if they defoliate, no sweat: I know figs will easily put out more leaves. At the right time of year, I don't care if a healthy maple defoliates. On a weak tree, I would be more careful, and scale insects can seriously weaken a tree. I might wash the tree every two weeks until I saw it rallying, and then spray it with something that would control the juvenile (crawler) stage, which, while invisible, is easy to kill.

Jim, is a "heard" of chickens a flock you *know* is there, but never see?

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Re: Scale on japanese maples

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