Biological control of Impatiens glandulifera in Great Britain
Impatiens glandulifera (Balsaminaceae: EPPO List of Invasive Alien Plants) is an invasive, annual species native to the Western Himalayas. It was originally introduced into the EPPO region as a garden ornamental and has spread throughout Europe. Management of such a widespread species using traditional methods can be both time consuming and expensive. Two strains (India and Pakistan) of the rust fungus Puccinia komarovii var. glanduliferae have been released as biological control agents against I. glandulifera in Great Britain, and the performance of the rust has been monitored across the release sites. P. komarovii var. glanduliferae is a macrocyclic pathogen with urediniospores which cycle on the leaves through the summer months, forming teliospores later in the season. The latter spore type overwinters and produces the basidiospores in the spring which infect the hypocotyl of the emerging seedlings. Although leaf infection levels are high in many sites across Great Britain, the rust has only successfully overwintered at four of the release sites. Experiments to assess the virulence of the two rust strains against different biotypes of I. glandulifera were conducted. The results highlight a large variation in susceptibility of urediniospore infection across I. glandulifera populations. In addition, the infectivity of basidiospores differed where some populations were fully susceptible to the urediniospore stage but immune to basidiospore infection. Looking towards the future, additional strains of the rust from the native range will need to be released in Great Britain to tackle resistant biotypes of I. glandulifera.
Sources
Pollard KM, Varia S, Seier MK, Ellison CA (2021) Battling the biotypes of balsam: the biological control of Impatiens glandulifera using the rust fungus Puccinia komarovii var. glandulifera in GB. Fungal Biology (early view). https://doi.org/10.1016/j.funbio.2021.03.005