Thrips

Thrips are small insects that are commonly found in garden plants, but occasionally turn up to infest houseplants during winter months. Their appearance can often be blamed on plants being brought indoors with insects, eggs or larvae on them, from which they can spread to other plants.

Thrips can be identified by their size; they are very small, less than a millimetre wide and only a couple millimetres long. There are several different types of thrips, but most of them are dark in colour. They are difficult to see because of their small size, but they will often appear in groups on buds and blossoms. They can run, fly weakly, and jump.

Thrips can also be identified by the damage they cause to plants. These insects feed by piercing and scraping leaves and flowers, causing damage that often looks silvery and spotted. Small, brownish specks are sometimes found, and are the bugs' droppings. 

Thrips often don't cause severe damage, but they can stunt young plants, cause a lot of damage to flowers, and transmit diseases between plants. Unfortunately, they are difficult to control, since eggs are inserted into plant tissues, and young and adult insects are adept at hiding in plants and soil. Washing plants, removing infested flowers and keeping growing temperatures cool and humidity high can help control them, but if the infested plant is not valuable, throwing it out may be the best way to keep the infestation from spreading. Insecticidal soaps or oils can be effective against thrips, but they must contact the insects. Blue or yellow sticky cards can alert you to the presence of thrips and provide some control of adult populations. If pesticides are desired, use a spray containing bifenthrin, permethrin, resmethrin, pyrethrins or neem oil every one to two weeks. 

6 comments:

  1. There are some thrips that are dark coloured like your picture, but none that jump as far as I know. The picture is of a springtail, probably in the family Isotomidae (see http://bugguide.net/node/view/249215).

    Springtails mostly feed on fungi, but some are pests of seedlings e.g. the Lucerne Flea - or the Garden Springtail. These pests usually have globular bodies:
    http://bugguide.net/node/view/85579

    Thrips have two pairs of bristle wings as adults and can fly off quickly, which may look like jumping. Their rear ends taper to a pointy bit too - while springtails have rounded bums with their jumping mechanism tucked under. BugGuide has good pictures of all kinds of thrips.

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  2. Dave - Thanks for catching my error! I have removed the inaccurate photos. That particular species of springtail happens to strongly resemble thrips, but you convinced me it wasn't. I have had thrips in my garden, so I assumed they hitched a ride inside on some chives I brought indoors for forcing. Most varieties of springtails I have seen in photos look nothing like what I saw, and the damage to the plants did seem more like damage from thrips than springtails, which apparently usually cause chewing damage at soil level. However, I threw out the infested plants, so I can't look more closely now.

    I believe that thrips can jump - my source for that is Jim Hole's book on houseplants in the What Grows Here series. But you might be right that their jumping is similar to flying. BugGuide is a very good source of photos to help identify your bugs, thanks for pointing me there.

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  3. Hi Cassandra,

    Re jumping thrips, we are in luck, the University of Alberta has one of the World's few specialists on the Thysanoptera: Emeritus Professor Bruce Heming. Bruce is not only a nice guy, but loves thrips (go figure!), and he says:

    "Yes. Some adult thrips, particularly in the subfamilies Panchaetothripinae and Dendrothripinae of the family Thripidae have greatly lengthened, lyre-shaped metafurcae extending forward into the mesothorax on which originate strong extracoxal depressor muscles of the hind trochanters. They're great jumpers and many die with the hind legs flexed forward under the body making it difficult to mount them dorsoventrally on slides."

    Cheers,

    Dave

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  4. I somehow, without having any indoor plants, have thrips all over the house. I thought they were springtails, and i have those too, but thrips are all over furniture, bedding, walls, etc despite cleaning for hours each day for the past 3 months. I have recently learned I have green algea growing behind windows. I imagine this is the thrips food source. I am moving out. I'm worried I might take them with me. Can thrips infest furniture, dogs, or people?

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  5. Yes, you can take them with you....but they will probably die off shortly. I have been fighting an "invisible" bug for years, which we finally determined to be thrips. They were entering my house through all the windows, even though they were fully functional, closed, locked. They were entering through the backside of the electric meter and phone box, and their debris was plentiful on all the wires hanging on my house. They are attracted to heat and white, as well as various scents.
    While it may be true that the adults are just biting to "taste" you, the nymphs are attracted to people, dogs, cats. In the case of an infestation and long term exposure, they cause severe hair loss, damage to connective tissue (bleeding gums, accelerated aging) and god only knows what else. Household members will succumb to the effects at varying times, which makes it hard to determine what's really happening. My youngest daughter was affected years before I was. In her case, severe acne was a side effect. They do NOT leave a raised welt or obvious bite, although severe infestations may cause welts and whiteheads that look like acne.
    The only thing we have found to help is rinsing (people and dogs) with 50/50 apple cider vinegar and water. There is no residual effect, but bathing dogs regularly will allow hair to regrow and keep them alive a lot longer.
    UNLESS you fail to seal your house extremely well. If they are getting in your house on their own (NOT uncommon), they will drive you insane and your dogs will be much worse than if they were left outside all day. Your dogs will NOT itch crazily like with fleas. The itch is more subtle and easier to ignore.
    If you have a short-haired animal, it's easy to check for thrips. Put the animal on a light colored sheet and brush vigorously on their back in front of their tail. Use a tightly bristled brush. After a few minutes, look at the sheet. The adults look like baby fleas (they're not) and the nymphs are opaque, very hard to see and very, very tiny. Springtails seem to be attracted to the thrips, as well as leaf footed bugs.
    We had to caulk our windows closed, squeeze caulk behind everything attached to exterior walls....everything.
    They have some type of sensory system where one puts out a substance and others are then attracted to that area.
    Think I'm crazy? Go outside and look CLOSELY at your exterior walls, windows, wires. See those little black spots? Thrip poop.
    Anonymous (above) I would bet my last dollar that thrip nymphs are entering your house on their own and biting you and your dogs. My male dog died from the infestation, and vets were no help.
    We were early victims, but I see this problem everywhere. "Experts" should educate themselves.

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    1. Thank you so much for typing this out. I was gardening today while the hubby is working, like usual I came inside to relax, about thirty minutes later I felt something on my forehead near my bangs when this bug fell out. I had no idea what it was or what it could do let alone why it was on me and trying to go in and out of my very thick hair and immediately thought it was lice until I noticed it was black and a totally different bug. Google had led me to this website and now I'm thankful to have knowledge about them since the hubby is an avid gardener. Now I know why he tells me not to garden during certain times, the house is protected from thrips and he shakes his clothes off outside and normally brushes me off, but I wasn't feeling well today and I guess it hitched a ride on my dark clothing. Now I know what to look out for and granted hubby is balding while my hair is turning gray, but not thinning.

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