Insects; Ragwort and the Cinnabar Moth

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Claire Browne
Insects; Ragwort and the Cinnabar Moth
When I first came to Britain, one of the first things I learned is that ragwort is poisonous to ponies.  V E R Y    D A N G E R O U S.   Kills ponies instantly if it gets into their hay - apparently they have enough brains not to eat it fresh in the pasture, but not to spit it out when eating hay.  Wicked weed, must be exterminated at all costs.  Interestingly, I had never heard this all the time I lived in America, where I was brought up around horses. So, when I got goats, I dug out any ragwort that got into our pasture, just in case it was poisonous to goats as well, and thought no more of it.   Then one day my son, Nick, told me the car park near the goat sanctuary was full of caterpillars.  'Wonderful,' I thought, 'just what I need for my Nature Table at the Buttercups Goat Sanctuary.'   So I went and had a look.   Lots and lots of ragwort in bloom in the car park, and full of the most amazing, big, fat,  tiger-yellow and black-striped caterpillars.   The caterpillars were from the Cinnabar Moth - a thumbnail-sized black and shocking pink moth which you occasionally see in the summer low in the grass in the Woodland Trust.    The caterpillars are poisonous because of the ragwort they have eaten, and so is the moth. I decided to keep a few caterpillars to see if they would make cocoons and hatch out the next summer.    Fortunately, I read a book about it:   the caterpillars don't spin themselves a cocoon on a branch -- they bury themselves in the ground to pupate.   So I turned them loose on a ragwort plant in the Woodland Trust.  Every year since then I have looked out for the caterpillars on the ragwort.    Some years there is lots and lots of ragwort and very few caterpillars.   Sometimes there is hardly any ragwort and lots and lots of caterpillars - and it is rather horrible what happens then.   This last summer (2015) there was very little ragwort in Mote Park but lots in Moore's Meadow, but only a few, skinny little caterpillars.   Further research says that the Cinnabar Moth is on the Rare Breeds list for insects; that ragwort is the host plant for 66 species, and although it is well known scientifically that ragwort is poisonous, nobody has every done a proper trial to see if it actually does kill ponies.  Ragwort on BWT land photographed in July 2016 by Claire Browne.

 

Editor
Ragwort on motorway verges

At the 2016 Annual Meeting Sharon explained that BWT do control ragwort in places where they are going to cut hay, but leave some for the cinnabar moths at the far end of Moore Meadow. 

I too, have kept ponies in the past, and have developed a strong impulse to pull up ragwort!   I notice on journeys that motorway verges are thick with ragwort. No hay cut there, and no animals there to be poisoned, so those plants will help the moths.  I wonder what the flying range of a cinnabar moth is!

 

 

 
Claire Browne
Ragwort and cinnabar moth

This year - 2017 - I have spent hours and hours checking the ragwort in Moore's Meadow, and have only managed to find  T H R E E  cinnabar moth  caterpillars.   That is not enough to sustain the population!   I am very concerned.

I looked up the cinnabar moth on the internet:    according to one site, this particular moth population has declined 86% in the last 35 years.    According to various other sites, the poor moth and its caterpillars are prey to a whole load of diseases, which may account for its severe decline.

So if you happen to have a bit of ragwort in your garden, think twice before pulling it up - it might just be somebody's lunch.