A Really Bad Way to Control Knotweed

In an effort to control one alien invader, the Brits now want to import another.

British scientists propose importing millions of Japanese sap-sucking psyllids to take down the island’s epidemic spread of Japanese knotweed, a highly opportunistic alien invader that tolerates a wide range of soils and extreme cold (-30 degrees Fahrenheit), and survives via roots that run 23 feet wide and almost 10 feet deep.

It’s a first for our cousins across the Pond – importing aliens to control an alien invasion – and you’d think they would know better after having witnessed, albeit secondhand, some of our more spectacular failures, like gypsy moths and Asian lady beetles.

The gypsy moth, first introduced to the continental U.S. as a strikebreaker for the slower and more finicky silkworm, has since proven it’s a glutton too lazy to make silk but perfectly willing to eat any green thing in sight.

The giant Asian ladybug, identifiable by its fewer spots and habit of coming inside in winter, was introduced in California in 1916. This species did as hoped, eating every aphid in sight. Unfortunately, this left the smaller, American lady bug on a permanent diet – a situation that currently threatens their continued existence.

The Oriental psyllids, also known as jumping plant lice, are sap-sucking insects who naturally control knotweed in Japan, where aeons of symbiotic development makes the latter the natural food of the former.

Their importation to the British Isles dismisses the ecological importance of this sort of symbiotic evolution, demonstrating yet again that science may have its eye on the ball while remaining completely ignorant of the net. This sort of end-goal blindness often leads to an ecosystem’s collapse, since native plants and insects didn’t ‘grow up’ developing any natural defenses against the invader.

This is the argument of British environmentalists, who foresee the dangers to Britain’s long-established and delicately balanced ecosphere. Unfortunately, the ravages of Japanese knotweed (which proliferates in the UK’s balmy climate and can grow to over 10 feet) push solutions before common sense. Agronomists estimate knotweed eradication will cost more than $2.7 billion dollars if herbicides have to be used. This doesn’t even take into account the environmental dangers and costs of herbicide remediation after the knotweed is banished.

British scientists counter that they have tested the oriental psyllids on nearly 100 crops and plants without observing any ill effects. The flaw in this logic is time. The testing covers less than a decade, and none of the scientists will be around to witness the adverse effects in 100 years, making this sort of heuristic problem-solving similar to the development of the atomic bomb.

Apparently these same scientists have also forgotten the 1930s cane toad fiasco, when Australia introduced the omnivorous amphibian to get rid of the cane beetle. These toads turned out to be better at breeding than eating beetles, and there are currently 200 million in northeast Australia, or 50 for every individual Queenslander. They not only complete with native species for food, but are poisonous when eaten, wiping out a lot of animals above them on the food chain.

How did the plant get introduced? Some gardener or horticulturalist reportedly brought a specimen of Japanese knotweed (Fallopia japonica) back to Britain about 1850, no doubt admiring its foliage and hardiness. The plant is capable of growing spectacularly, even in ‘waste’ ground, colonizing such unappealing scenery as abandoned parking lots, as it can grow through and break up solid concrete, or even damage buildings.

Its relentless spread can be attributed either to its hardiness or perhaps to the fact that knotweed is a commercial source of resveratrol supplements. Resveratrol, also found in red wine, is currently being promoted as the modern Fountain of Youth, and growers no doubt see it as the next really big cash crop.

I wish our neighbors across the Pond good luck with the project, but history has already proven time and again that introducing one alien species to eradicate or replace another has more negative benefits than positive ones, and leads to a chain of ‘fixes’ that never quite restore ecologies to their original balance.

I don’t want to accuse British horticulturalists of insanity (which Einstein defined as doing the same thing over and over and expecting different results), since this will be their first try, but I do think their optimism is unwarranted.

Site Disclaimer