To continue with the agricultural theme (well, almost). There is something of a horticultural problem abroad, only it's not abroad, it's right here in England. Way back in the early 19th century, an English traveller in Japan was very taken with a plant going by the name of fallopia japonica. So taken was he that he introduced the plant to England. His fellow Victorians also took a liking to it, with the result that it is now recognised as the most invasive weed in England and almost impossible to kill, certainly for the amateur gardener. This plant - Japanese knotweed - grows to a height of 13 feet and can split, and therefore grow through, concrete. So destructive is it that I understand building regulations require developers to eradicate it before they can start construction. Not that they always do. I believe Cornwall may be a "hot spot" and certainly the plant exists on the opposite side of the lane my brother lives in down in the far west. Despite its existence, a developer has built several houses on the land. But that is by the bye.
We are now given the good news that a solution has been found. The trouble is that it involves introducing another species alien to our shores - a 2mm long bug, Aphalara itadori, which breeds and feeds only on Japanese knotweed. The "experts" say they have carried out experiments and found that it will not eat 90 other species of plant. But what if it can't find knotweed and takes to eating, say, potatoes or beech trees?
That's the problem with introducing alien species: you never know just what will happen. Some of our waterways are over-run with mink after several animals escaped from farms and they have devastated the indiginous wild life. Parts of south London are infested with parakeets, again, following escapes. On the other hand, one of England's most succssful trees was introduced from somewhere in Asia (I forget just where) and the apple is now considered as English as, well, chicken korma.