Brown needles and silky web in hemlock

Discussion in 'Bugs and Crud' started by LWalton, Oct 6, 2017.

  1. LWalton

    LWalton New Member

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    Treated for HWA with soil injected imidacloprid earlier this year and now we're seeing this web-like substance (see pic). I won't embarrass myself with a guess.
     

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  2. JD3000

    JD3000 Well-Known Member

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    Spiders.

    But since you used Imid, look closely under magnification if need be for spider mite outbreaks.
     
  3. flyingsquirrel25

    flyingsquirrel25 Well-Known Member

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    X2 on Mite outbreak after imidicloprid treatment.
     
  4. JD3000

    JD3000 Well-Known Member

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    Might be mites.

    Hehehehee.

    I can't tell if there's stippling or not so I thought spiders first but one should look closer either way.
     
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  5. LWalton

    LWalton New Member

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    I didn't notice any stippling on the needles themselves, if that's what you're meaning. How are the the brown needle clumps produced - do the [spiders, mites, spidermites???] kill the needles (by sucking or chewing on them)? or do they just gather them (and the cause of needle browning and drop is different)?
     
  6. JD3000

    JD3000 Well-Known Member

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    I fugured the shed needles were from seasonal needle drop and they just stuck to the silk.
    Hard to say from a pic but there could be some other critter I'm not familiar with or some minor foliar fungal issue.
     
  7. LWalton

    LWalton New Member

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    Is mite damage a serious enough problem to warrant treatment? Perhaps it depends on the degree to which there's mite damage. If it is affecting >50% of the branches, what treatment do you guys use?
     
  8. JD3000

    JD3000 Well-Known Member

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    Abamectin is inexpensive but nasty stuff.

    Floramite and Hexygon have low toxicity and minimal impact on beneficials.

    Forbid works wonderfully but is expensive.

    Soaps, oils, neem oil.
     
  9. jed1124

    jed1124 Member

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    Horticultural oil at 2% will take care of your mites and adelgid. What rate did you apply the imidacloprid at?
    Keep in mind yearly applications of imidacloprid are not necessary to control adelgid. I've seen mite outbreaks from yearly apps.
    1 app at .2 oz. per inch of dbh should give you at least 5 years of control for adelgid.
     
  10. LWalton

    LWalton New Member

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    Great information. Thank you all!

    I believe we used Zenith 75 WSP at 3.2 oz/gal.
    How fast does the hort oil affect the mites? Is it important to spray both the upper and lower parts of the needles?
     
  11. JD3000

    JD3000 Well-Known Member

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    Yeah good coverage is necessary when using soaps and oils. Kills on contact only.
     
  12. jed1124

    jed1124 Member

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    Foliar apps of Zenieth 75wsp are labeled at 1 pack (1.6 oz.) per 300 gallons. I would go back and check your mix rate. If you are using it that high that would explain the mite outbreak.
    Hort oil will kill mites on contact but has no residual effect. Coverage is essential to good control.
     
  13. LWalton

    LWalton New Member

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    I could be wrong about app rate, but we were doing soil injections with the zenith.
     
  14. jed1124

    jed1124 Member

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    Check how many oz. you're using per inch and get back to us. I don't do premix solutions with imidacloprid it's to easy to over dose. .2 oz per inch of dbh is where you want to be.
     
  15. LWalton

    LWalton New Member

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    I believe we did 1 packet (1.6oz) in a gallon of water to treat dbh of 24 inches, which equates to 0.067 oz/inch. Perhaps we're way to low and should be treated dbh of 8 inches with the same 1 gallon solution? Label appears to indicate 0.1-0.2 oz/inch range, so 1 packet should treat 8-16 inches DBH?
     
  16. JD3000

    JD3000 Well-Known Member

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    This is why using the 2F formulation is much easier.
     
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  17. jed1124

    jed1124 Member

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    Yes, one pack treats 8" of dbh for most insects.
    Flat headed bores like eab and bbb on trees over 15" dbh should get the high rate of .4 Oz per inch.
     

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