A well-balanced article about the biological control of Japanese knotweed was published today in a British newspaper. Most articles about the release of the Japanese knotweed psyllid (Aphalara itadori, pictured) that appeared last year were either dismissive of the idea of releasing a non-native insect to combat another non-native species, often on the grounds that the selected agents will also damage native species. Or the articles just copied bits of press statements.
Wild gingers, Hedychium spp., belong to the same family as edible ginger (Zingiber officinale), but they have no culinary value. Native to moist tropical forests of Central and Southeastern Asia, they are cultivated the world over as ornamentals. Their large, glossy leaves flare out around their tall reedy stems and their orchid-like, showy blossoms come in a breathtaking array of colours, exuding a heady perfume. Such is their aesthetic appeal, that they are showcased in the finest Hawaiian leis (floral and leaf garlands). Their scientific name, Hedychium (pronounced “heh-DIK-ee-um”), is derived from the greek “hedys” meaning sweet and “chion” meaning snow and is based on the type species for the genus Hedychium coronarium (white ginger), the sweetly fragrant and best known ornamental ginger, which Cuba adopted as their official national flower in the 19th Century as a symbol of purity, rebelliousness and independence.
But in parts of its introduced range, such as Hawaii, New Zealand, Australia, South Africa, La Réunion and the Macaronesian Archipelagos, beauty has turned to beast; the very characteristics which gained them favour in gardens, such as hardiness and capacity for rapid, vegetative growth, have allowed them to naturalise in the wild and smother many unique and specialised communities, threatening delicate ecosystems, especially forest ground flora and associated fauna. In particular, Kahili ginger, Hedychium gardnerianum has earned a place as one of the world’s 100 worst invasive alien species and biological control is considered the only practical and sustainable approach for the long-term management of large infestations in native forests.