Compare and Contrast

Two members of the polygonacae family. On the left Broad Leaved Dock, its leaves eaten away and reduced to skellingtons (or skeletons if you prefer words written correctly).

On the right Japanese Knotweed, growing in its pristine pomp. It's unmblemished as the Centre Court at Wimbledon before they inexplicably allow ‘tennis players’ to run on it.

The difference is, of course, one is a native plant the other is an alien. All native plants have their own ‘pests and diseases’. These are organisms that have evolved alongside the plant, quite often specialising in just the one foodplant. Usually there is a balance, the plants aren’t wiped out but are kept in check by their pests.

Japanese Knotweed has its fair share of diseases in its place of origin. As an alien, on the other hand, it has no such enemies, so it grows rampantly -  an unstoppable army - the Mongol Hordes of the plant world.

This, in turn, gives the incomers a massive advantage over their homegrown rivals. The natives get out-competed.

I was struck by this contrast while on my patch walk. There were stands of the Knotweed, as well Himalayan Balsam, to which the same thing applies. Then there were sorry looking, moth eaten – literally in some cases – leaves of the natives. It’s enough to give Nigel Farage and his ilk palpitations.

These two species were intentionally  introduced in Britain around the middle of 19th century -  because of their "herculean proportions" and "splendid invasiveness". With the benefit of hindsight this is looking like a Big Botanical Blunder.

"I got my pest-and-disease eye in", isn’t a phrase I expect to ever need again. However, on my walk, I got my pest-and-disease eye in. I started to see all manner of leaf-mines, rusts, blights, leaf curls and little green men (just checking you’re stlll reading).
Lavae of the Green Dock Beetle on Broad Leaved Dock
Mines of a fly - The Holly Leaf Miner (Phytomyza ilicis). Some Moth, Beetle and Fly species have lavae which are leaf miners. They  are protected from predators and plant defenses by feeding within the tissues of the leaves themselves.
Coltsfoot Rust Gall (Puccinia poarum) Top side and under side of Coltsfoot. It is  a 'Heteroecious' fungal parasite meaning it has two distinct hosts for different parts of its life cycle - the other host being grasses.

Adult Green Dock Beetle
Get this