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  • 1 Post By Cjcorner
  • 1 Post By coeruleo

Black thrips - a difficult problem

This is a discussion on Black thrips - a difficult problem within the General Orchid Culture forums, part of the Orchid Culture category; ...

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  1. #1
    Dorsetman's Avatar
    Dorsetman is online now Senior Member
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    Geoff Hands
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    Cattleya ?
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    Oct 2010
    England, South coast.
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    Default Black thrips - a difficult problem

    I have a thrips infestation ; no doubt at all as to what it is, although it took me a long time to be sure. Now disfiguring my cymbidiums and oncidiums, ( leaves) and destroying flower buds generally.
    For maybe 4 or 5 months after first spotting it, I sprayed with half a dozen different insecticides, usually at the recommended intervals - no less than 10 days. I also tried wiping all leaves with cotton wool balls dipped in insecticide ( takes a long time with 1500 plants), and a dip in a bucket of the stuff to kill any in the compost.And then I tried a biological fix - but maybe the one I used didnít like black thrips, and only the yellow kind - a different species. But still they came back and spread and got worse and worse. I only actually saw an adult insect a few days ago - it showed up well on a yellow cymbidium bud.
    Now I reckon that my problem is the very short life-cycle. According to one website the nymphs feed for only a few days - less than a week, before they drop off, onto the ground, compost or whatever, to undergo two further instars ( the right word for the equivalent of the chrysalis stage with butterflies) before the adults emerge ready to lay eggs and start the next cycle going - moreover they donít stop to mate. Male thrips donít exist ( how boring for them).
    So I have now set a program of spraying every 3-4 days, changing the chemicals and working through six different ones I can find on the market here in UK available to amateurs, using each one twice. This should deal with resistance, and short life span/rapid cycling of generations. I also have glue traps hung throughout the greenhouse - and catch a lot of small black things - whether any are thrips, or just moss flies - too difficult to tell.
    The only and major snag is that I have already had some loss of new growths through rot, from spray collecting in new growths even in the summer - and it is winter here now. I intend to turn up the heat, to say at least 20 just for a few hours after each spraying before going back to my usual settings. I also plan to add some Physan substitute ( canít buy Physan in Europe) in the hope of cutting down on rot causing bacteria , but I have no better ideas.
    If anyone else has - I am all ears !

  2. #2
    Cjcorner's Avatar
    Cjcorner is offline Senior Member
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    West of Tampa, FL
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    Have you tried Listerine? I hear that works as an anti-fungal, anti-bacterial pretty well. And for the buggies...I mix up a spray bottle with rubbing alcohol in addition to a "take down" bug spray. I use something like a toothpick or skewer to get it down into the leaf axils and then turn up the heater and fans to help them dry. Good luck buddy, we had something like that last winter here and some nurseries lost entire collections. I ended up losing about 1/4 of my collection.

  3. #3
    coeruleo's Avatar
    coeruleo is offline Night Bloomer
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    Apr 2012
    Los Angeles, CA


    ugh! i think those are the same thrips we get out here in california. almost impossible to see (i've been calling them orchid fleas for years) until too late. they annihilate any soft orchids like ludisias in a day. they go for cattleya, epidendrum, some oncidiums and others. they are rough on a collection. the only thing i can do is frequent sprays of neem in the evenings (it burns in the sun) and regular doses of systemics. they are why i had given up on orchids for about 7 years or so... they destroyed my huge collection of epis! i also have been using diatomaceous earth, which makes the plants dusty looking, but might be helping. since i only have about 150 plants, it is easier on me to take them to the sink or shower and actually use water to blast away the bugs, then treat with neem, then water with systemics. normally only a bother in summer, thankfully.

  4. #4
    phalspital's Avatar
    phalspital is offline Senior Member
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    Coastal Florida/Switzerland


    The only big-box spray I could find that specifically says it's effective against thrips was an Ortho product for roses and flowers. It contains acetamiprid .006% and claims to work on contact and systemically. I believe it has finally killed most of the thrips, given that I can't find any adults even with a magnifying glass. However, I had to cut off 10 spikes that had already been deformed. I hope they will still spike again, as it was early in the game. I did notice that the white phals (Yukidians) seemed to be uniformly hit harder...the surviving uneaten spikes are all purples or golden with burgundy speckles. Is it a weakness of the Yukidians? Do the thrips detect white-flowered plants even before the flowers appear? I know they love my gardenias!

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