vomiting caterpillars – advice please

  • Creator
  • #46585


    I’m still new at this, learning as I go but need some advice please – questions are at end of post.
    (and also apologies for missing several replies re:cats needing food back last March! I forgot to check the post again after my own reply)

    From the top: started February 2015 with 2 plants in garden, 6 indoors; 8 caterpillars, 4 died, 4 pupated but none hatched. Probably good I didn’t get more cats (helicopter parenting). Plants all survived winter outdoors in tubs. Used Biofeed, massive spring growth.

    Spring 2015: major aphid infestation, cleared by hand; many visiting female monarchs; couldn’t make myself cull, had 65ish caterpillars so bought more plants, new total = 27 plants – about 30 hatched butterflies, several failures, probably unrecognised OE. Lesson = cull eggs.

    Summer 2015: re-potted new swan plants + 3 tubs of “butterfly mix” flowers from seed. (Used commercial fertiliser not just organic Biofeed, don’t think the plants were as healthy)

    Christmas 2015: Many many 2nd gen females; didn’t cull enough eggs = 437 caterpillars! Obviously not enough plants so as I ran out of leaves I’ve been doing *major* transfers of cats, from tiny 2mm newbies up to 5cm ready-to-pupate; initially *really* careful to take the scrap of leaf NOT touching caterpillars, started rushing too much and handling smaller and smaller cats.

    I’ve read things on OE + high level toxins in plants + pesticide residues on/in plants… I know now (a) poor hygiene (b) stress (c) overcrowding all raise cat mortality rate; I also know now that I need to space the swan plants in smaller clumps further apart – and net most of them away from butterflies; I’m keeping a watch out for wasps, strange bugs and spiders. I have seedling trays of Cassavica plants but prob. won’t use them even if they sprout; NO chemical sprays near my garden OR any indoor plants. I’m also going to be inspecting the chrysalises regularly for black spots, and the hatching butterflies for deformation. AND… I’ll be looking at the online habitat course!

    Latest problem: last 4 stems with leaves, I’ve been transferring ALL remaining cats there but have had cats vomiting green liquid on themselves and each other – from 5th instar size down to 2cm – and/or falling off the plants and writhing/curling back on themselves (euthanised in freezer). The plants themselves are coated in dried green/brown yuk, both stems & leaves. Oh – and this batch of cats have been eating the flowers and the seeds as well as leaves and stem tips.

    Can you guys please advise me: (1) is there any likelihood that this green vomit is OE? It seems more like poisoning symptoms. I don’t want to “scorched earth” my plants and the current generation of caterpillars if it’s unnecessary. (2) if this *is* poisoning, would the yuk coating the plant be toxic to the other cats in itself? (3) if I sponge the plant stems now before they rejuvenate do I need soap, or dilute bleach, or plain water? (4) if I do use dilute bleach will runoff kill my plants?

    Any links to articles/resources, hints, tips you could pass on would be much appreciated. I want to let the monarchs DIY as much as possible.

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  • Author
  • #46604


    Thank you, it’s good to hear from someone with more experience. It’s definitely time to clear the frass, wash the plants, move and net them – I saw a bright new monarch today but it didn’t linger (maybe because I only have potted stumps right now).

    *sad* Unfortunately the last 15 cats on the one plant are all badly poisoned and some of the ones I moved to newer plants didn’t recover, too much exposure. Odd, its just 2 plants side by side although I had a ring of 10 plants there, and only in the last fortnight. I’ll keep those 2 aside for next season.

    Thanks again. The poisoned caterpillars were awful but the ones on plants inside and the ones already pupating should be OK (fingers crossed).



    Your latest post may indicate another problem also, “overcrowded plants” can lead to disease, in which case the frass should be removed.



    ” – but have had cats vomiting green liquid on themselves and each other – from 5th instar size down to 2cm – and/or falling off the plants and writhing/curling back on themselves – ”
    1. The above is a classic description of poisoned caterpillars, i.e. insecticide, herbicide, etc.
    2. Yes
    3. A couple of good hose downs with plain water should wash off the residue. Is it possible wind born spray from a neighbouring property may be the cause. However if it is a systemic spray, hosing down will not be effective, as it is absorbed into the plant and remains active for weeks. Fresh plants would be my recommendation.
    4. Probably, depending on the strength.



    Oh, and another question about the frass – overcrowded plants means piles of poop around the base of each plant; should I be attempting to clear some of it away, or just leave it and mulch?

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