So what's the problem?
Japanese knotweed is a fast-growing plant species that is causing a great deal of damage in Europe and North America. This herbaceous plant forms dense, impenetrable thickets comprising of stalks 8 – 12 feet tall. Originally, as the name suggests, the plant was imported from Japan as an ornamental, and in some areas of North America it can still be purchased. The plant soon escaped from gardens and has spread rapidly, out-competing many native species along the way. In Japan the plant has evolved with an array of natural enemies, from fungal diseases to predatory insects, which help to control the growth and spread of the plant naturally. But in the USA and Canada none of these specialist natural enemies are present and so the knotweed is literally out of control.
What is this project doing?
Scientists from CABI have already carried out a considerable amount of research focussing on the same problem in Europe. The main drive of research has been to learn about the biology of the plant and its natural enemies in its native range – Japan. The next step involves selecting those arthropods or fungi with the most potential from the many that are to be found on the target plant. This involves vigorous screening to find candidates that are highly damaging, restricted to the knotweed plants and that do not pose any threat to valued species. The end-goal is to find a suitable species that could be reared and released in North America to help control the spread and growth of knotweed without causing any negative environmental effects.
Results so far
Surveys in Japan identified around 200 natural enemies of knotweed and after extensive testing two species have emerged that both show great potential for use as a natural control agent. Firstly, there is the plant-feeding insect (a type of psyllid) Aphalara itadori. This insect has shown a remarkable specificity with a very high fidelity to knotweed when laying eggs, and any eggs laid on non-targets are unable to develop on the plant species so far tested. A. itadori has killed plants completely in the lab, and even low numbers of the insect reduce the height and leaf area of the plant. The second candidate is a Mycosphaerella species of leaf-spot fungus, which is also proving to be highly specific to Japanese knotweed.
Sean T Murphy
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Biological control of houndstongue
Revisiting biological control of field bindweed
Searching for a biological control for Dyer's Woad
Controlling Japanese knotweed in Great Britain
Stemming the spread of Russian olive
Keeping Florida’s waterways unclogged
by A Bailey, D Chandler, W Grant, J Greaves, G Prince, M Tatchell
28 October 2010
Hardback / 9781845935597 / £75.00 / $145.00 / €100.00
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