Whilst we always seem to be asked how to kill Ragwort we also need to bear in mind that it supports a wide range of wildlife; over 40 types of insect use it as their food source or habitat and it is also a very good source of nectar. One particular insect that loves Ragwort is the Cinnabar moth caterpillar, a very colourful little thing that will naturally predate on Ragwort and is widely visible at this time of year.
Whilst Ragwort is toxic to livestock and horses, this same toxin not only doesn’t affect the caterpillars, it benefits them! As the caterpillar eats the Ragwort they become toxic themselves and, together with their colourful stripes, this becomes a warning to predators that they are poisonous and taste terrible!
The young caterpillars are vulnerable as they have not yet built up a toxicity and so will cluster at the base of the Ragwort plants until they are big enough to start moving up the plant. A single plant can host several hundred caterpillars meaning the leaves are quickly stripped. The sheer numbers of caterpillars on a single plant also creates a lot of competition for food which leads the caterpillars to be more aggressive- they will actually resort to cannibalism to keep themselves fed!
Once they have developed fully, which takes about a month, they will head back down to the base of the plant and ready themselves to pupate. They will pupate into a cocoon and stay here all winter until they metamorphosise into the very pretty red and black adult moth.
So, before we start pulling and spraying Ragwort off, please bear in mind that it is a host for a multitude of different insects and think, does it really matter if it carries on growing where it is?
For more information on Ragwort, please feel free to get in touch on 01522 246491.
Ollie Wright
