There are many deadly plants in the world. Competition and Darwinian Theory tell us that it is because this makes them fitter for a given task.
Ragwort kills many horses every year, along with other animals, across the UK. Japanese knotweed is an aggressive pest plant, capable of destroying a house’s foundations and growing a centimetre in an hour.
I propose that we genetically engineer a few of these pest species to reduce the problem. It is really a twist on conventional bio-controls, and could probably be achieved by conventional breeding within just a few generations in some cases.
Take ragwort, and produce a more virulent strain, but without the toxic alkaloids. Release this into the wild, and, since the yellow peril that is toxic ragwort has to waste resources becoming toxic, the new strain, identical in every other way, should be able to compete with it. The new strain won’t get eaten much, since most animals are wont to avoid a bellyfull of nasty plant that made them sick before, whilst the cross-breeding of the two strains should produce fewer wild plants that are a hazard. After a few years, the bright yellow ragwort might be seen as just another nice weed, like buttercup and dandylions.
Of course, this trick totally won’t work against the Japanense Knotweed, as it merely grows very, very quickly, spreads easily, and is almost un-killable. It has no defence mechanism except proliferation, and heavy grazing can even be used to control it, before it is well rooted in. (Interestingly, every single plant in the UK in a clone of a single knotweed plant, making it the biggest female in the world, by mass.)
A different approach is needed for this invader, and I will have to have a think about it…