Caterpillars keep dropping from plant

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    I have 3 plants with 4 x near mature caterpillers. Of late they are dropping from the plant and appear near dead (very lethargic). Any reason for this? No fertiliser used and no insecticides or other sprays applied. My Child is stressing over her brood. Thanks. Iain

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    Also observed another thing. Having observed caterpillars seeing them chew themselves off their own plant, rather like a man sawing himself off his own branch. Also one caterpillar may be chewing happily away and another is behind it also chewing the joining part off so a caterpillar is destined to fall…




    Update…Two of the remaining caterpillers have regained full health and colour. The other two have continued to remain on the plants but look to be ‘compacted’ and faded. It appears that after several light showers, the problem may have been rectified leading me to believe that the plants/pillers may indeed have been affected by air-borne pesticides or the like. Cheers



    Hi Iain,
    A while back I had some problems with caterpillars, they dropped off the kapok plant I had and convulsed. Now, I’ve been feeding caterpillars on kapok plant for 3 yrs and see no reason to suspect kapok. I took it these creatures were diseased. When I wiped the rim of the bucket I saw the reason for the caterpillars fatal illness. Some unidentified black insects were attacking the caterpillars and I cleaned the lot up – no problems ever since.
    Make sure you clean out ants and spider webs too, as you don’t know what these creatures do to caterpillars.

    Hope you have more luck with them.




    Thanks guys
    I’ll keep you posted. I’ve just reinstated several ‘pillers back on the foliage following this mornings check. I feel like a mother hen!



    Iain — if this keeps occuring, would be a good idea to do as Carol says, and see if flies do emerge from the caterpillar(s). Obviously, then, each dead/dying caterpillar will be increasing the number of predators in your immediate vicinity and it would be worthwhile removing any caterpillars to a new location – and ensure that lethargic or dead ones are kept in a separate location again. You’ve got a project on your hands!



    And more… This is from Carol Cullar who is Executive Director of the Rio Bravo Nature Center Foundation, in Texas. At the end of the email, she mentions a website, and this is invaluable.

    Iain, it would be interesting to keep one of the dead caterpillars in a jar and see if the flies do emerge.

    <<<Nuclear polyhedrosis virus killed my home reared monarchs for a couple of growing seasons. When I learned what it was, I cleaned all my work surfaces and containers with a strong bleach water, including the containers I was rearing in, glass table top, and microscope. I’ve heard that others also use a milder solution to rinse each leaf [of course with a plain water rinse after that] before they feed. I didn’t do that because I harvest the leaves from the wild in a variety of locations. When you are rearing monarchs on potted plants or ones that survive perennially, they could be getting it from the soil around the old plant.

    Under the microscope, my lethargic monarchs appeared to have reddish brown striations developing beneath the outter layer of skin.

    We also had some lethargic monarchs that were infested with tachinid fly larvae. I isolated those and was able to capture the emerged egg case and kept the fly till it died, so I now have a specimen to show.

    This is a good site to visit and recommend:






    Hi Iain,

    Here’s the first response, from a UK butterfly expert:

    <<<Hi Jacqui,

    It is difficult to be sure, but if it isn’t some kind of poison then it
    sounds like a disease. The symptoms you describe are similar to those
    described for a disease originally discovered in silkworms and given the
    french name “Flacherie”. This can either be caused by a bacterium in the
    groups of species which includes both the infamous Bt insecticide and
    Anthrax which affects mammals, or it can be caused by a virus.

    Sadly, if this is the case, there is probably very little that can be
    done. I have heard of antibiotics working against bacterial infections
    and of a garlic extract being used with Assam silkworms ( A wild
    silkmoth similar to the Polyphemus moth.) However, it is probably too

    There are a number of other diseases known and there are probably many
    more to be discovered. We know very little about the diseases of

    I’m sorry to hear about a child being distressed over this perhaps there
    is a benefit, if the child is old enough, to get an educational lesson
    by studying the work of Louis Pasteur, the famous french scientist who
    discovered the cause of bacterial flacherie. It was the first time that
    a germ had been shown to cause a disease in any kind of animal. This
    pioneering work is a cornerstone of modern medicine and has led to the
    saving millions of lives over the years. All because someone was
    interested in studying caterpillars.

    Incidentally just in case I cause alarm, despite some of these
    caterpillar diseases being related to Anthrax they pose no risk at all
    to humans as they lack the necessary genes to cause problems in a
    mammalian body. You can’t get sick from handling a sick caterpillar. I
    have had disease outbreaks in all sorts of species over the years and I
    am still very much healthy.

    Neil Jones>>>



    Thanks for the comments. The ‘pillers were quite happy for the first few weeks of their growth. The plants have been undercover (front porch/veranda) and sheltered from inclement weather etc. 10 had been consumed by paper wasps 4-days prior to this location so I was wondering if there was a legacy to this??

    I relocate the ‘pillers back into the foliage but they repeat their lemming activities once I turn my back.



    Hello Iain — I’ve never heard anything like this happening before, but it sounds environmental (e.g. spray drift). This is what was happening to the caterpillars of a friend of mine, who had bought plants which had been sprayed from a garden centre.

    Now I’m not saying that’s what has happened to yours – but in my garden, as an example, I would suspect the neighbour’s had possibly had incinerated some plastic etc, etc.

    One thing you could try is moving the caterpillars onto a branch from a different plant in a safe location, like a different part of the garden or even indoors, in a back porch, or on a deck or somewhere. Also, I’d water the plants well with a hose, in the evening or on a dull day when it’s not hot.

    I will also make further inquiries and let you know if I find out any more indicators. I’ll leave a message in here if I do find out more.

    Sorry I can’t be of more help for now.




    Iain, are they wanting to go up high to ‘roost’? I find sometimes with my caterpillars that if they cannot get up high they drop down to find some way of getting up high. In amongst my swan plant I put sticks so they can get up to turn into chrysali… I don’t know but Jacqui may be able to answer you…. she is a bit busy at present.

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