4-5th instar caterpillars dying – thoughts?

  • Creator
  • #52444


    Received this message on our FB page, and while I feel for the sender of the message, I am way behind on my work to spend much time on this… so wonder if you people out there can advise her please? Quote:

    Hi there. I wondered if you’ve had any issues this season with a disease where your 5th instar cats actually shrivel/shrink down to a third of the size.. then basically stop functioning & eventually die. I’ve had ,whatever this, wipe out my cats in captivity 😞

    Would you suggest keeping your cats in captivity? Or raising them in the garden? I was trying to keep them safe from predators, but I’ve had a higher rate of death from this disease, despite doing my best to keep the enclosure clean. 🙁

    I’m in Taranaki. I raised around 70 healthy butterflies this season.. then this last cycle of cats has become infected with something.. I can’t figure it out 😞 Seems to hit them at 4th & 5th instar.

    They refuse food.. just become totally inactive.. then I find them all shrunk down to a third of their size.. all squashed up. They slowly writhe around in this state & I’d left them on a piece of netting originally.. thinking they might be pupating early & hadn’t attached.. but then within a day they’re dead. I’m now separating any symptomatic ones.

    My 5th instars are in an enclosure with moth vine (I’m running very low on food), which got the other 70 through to healthy butterflies. It’s unsprayed. This disease is infecting those on the milkweed & on the moth vine.

    I’ve been reading about OE. Do we have this in NZ?

    And my milkweed is unsprayed. They’re living on seedlings that grew from last year’s trees, which were sadly destroyed by that bloody yellow aphid!
    I’m not sure if this is a help.. but here’s how they look when they’ve passed away.

    dead caterpillar

    They can be big fat 5th instars & within a couple of days, they become this 😞

    This cycle of cats, I had about 40.. & they’ve just been almost entirely wiped out. I just squashed a chrysalis that was COVERED in black dots, which yesterday I learned was the protozoans?

    I’m just a beginner. A real beginner. My trees were destroyed by yellow aphid & I spent a fortune on new plants.. but they weren’t enough to feed all the hungry cats.. & so I kept the 5th instars in a fish tank, with netting across the top & fed them moth vine to get them through. No deformities & the chrysalis seemed fine.

    THIS cycle of caterpillars is where there’s been an outbreak somehow. Finding dead caterpillars every day. I only learnt about the bleaching solutions yesterday & found the video posted on the forum a few years back from North America.

    I had been keeping my 1-4th instar cats in my butterfly cage eating fresh seedlings. There’s no spray contamination on the plants or moth vine.. no roof work done. I realise it’s purely my fault. I haven’t been sterilizing the enclosures when I find disease, not aware it would be spreading like wildfire. Trying to help the population has cost the lives of countless caterpillars now. I will try my best to keep this problem contained to my back yard 😢

    It’s unfortunate that once you discover an issue.. start researching.. you realise the problem has gotten out of hand because of what you’ve done, or haven’t done. I commend you & the group for working so incredibly hard for these creatures. Hope that one day I can say I am actually helping them too.

    Hope someone can help her…


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  • Author
  • #52455


    Sounds pretty dire. are you feeding the plants anything? I know some things fed to the plant will kill the caterpillar. I’m wary of even things that should in theory be ok now and prefer just to give the plant water. And if the plant is potted make sure the plant is not sitting in too much water, the plant seems to start producing yellow leaves if the plant can’t drain properly.
    I’ve had some cats just stop eating and die recently and in hindsight its been after I’ve fed the plants coffee grinds to try and revive them after they have been stripped. Might not be the cause but it was a consistent factor. Worm pee seems to be ok.


    rob cooper

    im not sure what you mean about them living off the seedlings destroyed by the aphid so what are they living off?


    rob cooper

    yea not sure we lucky i suppose got over 170 away now ok do you have neigbours have they been spraing thats a possiblty onl thing i gan think of best of luck

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