Two, four, no, ten pests in one!

Nine Broad Mites hitch a ride on a whitefly
Nine Broad Mites hitch a ride on a whitefly

I guess I’m getting giddy from too much time humped over a computer or a microscope and a lack of sun and warmth (it’s a cold, late spring here in Alberta).  So here is something from a sunnier clime, or rather somethings.  The Bemisia whitefly in this image was sent to me by some colleagues in Toowoomba, Queensland (currently with a clear 8C autumn night and a weekend with predicted highs of 23 C, beating the May Long Weekend in Edmonton by 4-5 degrees).  Unfortunately, the whitefly was not covered with parasites, but with the infamous Broad Mite Polyphagotarsonemus latus (Banks) (Prostigmata: Tarsonemidae), a plant pest with, as you might guess from the generic name, a broad host range.  However, I think the common name comes from it being rather tubby (0.17 x 0.10 mm).

 Like many mites, the life history of the Broad Mite is amazing.  For one thing, they have reduced their life cycle to the almost the bare minimum – egg, larva, adult – cutting out all three nymphal stages.  At a constant temperature of 27 C, this mite can go through a complete generation, egg to egg, in 3 days and summer generation times in the field are typically 4-5 days.  As the larvae and adults feed, they distort leaf tissue into folds and bumps that protects them from weather and predators – not quite as fancy as the gall mites in the Eriophyoidea, but on their way there.

 Male Broad Mites have a large sucker-like genital capsule sticking out their rear end and they use this to hold onto inactive larvae – pharate females that are finishing up their development within the larval skin.  This looks a bit strange – the pharate female crosses the male T – and has fooled several entomologists into thinking they were observing an act of predation.  Nope, just males that want to make sure they alone go on a female’s first date.  This type of precopulatory guarding has evolved numerous times within the Acari, and in this case is associated with a male aedeagus and a female secondary sperm transfer system.  This makes quite a contrast to the oribatid mites with which I am currently working.  Male oribatids wander around depositing spermatophores on the substrate wherever they feel like it, whether or not females are around, and make no effort to contact, let alone guard, a female.  Perhaps that is one reason that 10% of oribatid mite species appear to be thelytokous (i.e. all female and parthenogenetic).

 As you may know, whiteflies are rather small, but not so small that a heap of broad mites can’t hitch a ride.  Mites lack wings, so if they want to get between patchy habitats, they have to come up with an alternative means of transportation.  A surprising number, including many members of the Broad Mite’s family (Tarsonemidae), simply orient to a stiff breeze and let go to become part of the aerial plankton.  That seems pretty inefficient if you have a specific place you’d really like to get before you dehydrate or starve, but I don’t know that climbing on such a tiny and seemingly inefficient flier as a whitefly is much better.

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11 Responses to “Two, four, no, ten pests in one!”

  1. Adrian Thysse Says:

    Fascinating, as usual. Thanks!

  2. Mike from Ottawa Says:

    I have nothing cogent or clever to say, just a remark about the blog in general: WOW!

    Thanks!

  3. Linda Says:

    Hi,

    I work in a greenhouse in Toronto. And today, I was looking at some damaged Jerusalem Cherry (Pepper) plants. Although it looked like mite damage, I thought it was thrips because random plants were damaged. I even said to my boss “this looks like the work of a flying insect”. Then we found some broadmites on the plants.

    This picture of the broadmite on the whitefly explains everything.

    Thank you so much!!! I have sent a copy of this link to my boss and some of my co-workers. Amazing! Really made my day.

  4. Warren Says:

    Re: parthenogenetic oribatids: has Wolbachia been investigated?

  5. A question Says:

    Hi this is Rafa. Im conduction a research project on pepper plants and my plants get plagued by whiteflies. I friend specilalist in whiteflies said that whiteflies had “shoes” and when she observed the flies down the microscope she noted that had mites. I wonder if broad mite is the only one dispersed by whiteflies?

    • macromite Says:

      Hi Rafa,

      Broad Mite is the only mite that I know of that has been found phoretic on whiteflies; and of course, it is a major pest of capsicum, so I think the ‘shoes’ are likely Polyphagotarsonemus latus. However, phoresy is common in the Tarsonemidae, so it is possible that some innocuous fungus-feeding tarsonemids may also hitch rides on whiteflies. Also, may hypopi of Astigmata are rather non-specific in their choice of a carrier. Adult female spider mites (the dispersal stage) are not known to be phoretic and whiteflies are on the small side for such relatively large mites to hitch a ride. The same goes for phytoseiid mites – I think they’d look more like over-sized baggage than shoes. Eriophyoids are not usually phoretic (the only case I know of is flower bud-gallers that hitch rides on bees), but it is always good to keep an open mind (and to have the mites identified).

      Cheers,

      Macromite

  6. Benjamin Smith Says:

    This may be an odd request, but I would like to use your image of the whitefly with the broad mites in a “macro” contest on cracked.com. With your permission, I would use your image and add some text to it. Here is a link to the contest and its details:
    http://www.cracked.com/forums/topic/169669/24200-image-macro-contest-microscopic-horrors-in-around-your-house-right-now

    Please let me know if I have your permission.

    Thanks,

    Ben

  7. gymnosperm Says:

    I would also like permission to use that amazing photo. I’m writing a post about red blotch, a viral disease of grapevines that is epidemic in Northern California. It is what I bet will eventually be a new genus of Geminiviridae but the known vectors (whiteflies and hoppers) are not panning out.

    The distribution of new infections very strongly suggests a “road effect” that has led me to suspect mites as a vector. I have found infections in wild grape confined (for now) to road corridors miles from any vineyards. During harvest truckloads of grapes from many vineyards pass along these roads.

    Our local well known mites, Pacific and Willamette, tend to reach population peaks in mid season and be in decline by harvest. These guys are visible to the naked eye and get attention, but we also have two microscopic mites, Erineum and Brevipalpus whose populations peak at harvest.

    My suspicions lead to Brevipalpus because of its long rap sheet of vectoring at least four different families of viruses. Of course, I could be accused of virus profiling…

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