Biological control of Impatiens glandulifera
The macrocyclic rust fungus Puccinia komarovii var glanduliferae was released as a biological control agent against Impatiens glandulifera (Balsaminaceae; EPPO List of Invasive Alien Plants) at a limited number of sites in the United Kingdom in 2014. In 2015, a nationwide release programme was initiated at over 25 sites. At most of these sites the rust spread to infect field plants in the close vicinity though infection (pustule size) was lower compared to that seen under greenhouse conditions. In addition, there was variation in infection between sites indicating differences in susceptibility between biotypes of the plant. In 2016, the focus of the research was to establish the rust in intensively monitored sites over the course of the season and to explore variation in susceptibility between populations. To investigate susceptibility, plants were grown from seed collected from 18 sites in England and Wales and infected with rust. Although the results are still under analysis, there is a clear indication that there is significant genetic variation within the population of I. glandulifera in England and Wales and this is reflected by the variation in susceptibility of plants to the rust. With this in mind, more than one strain of the rust may be required to control the plant nationally and to this effect a rust isolate collected from Pakistan in 2006 has been tested against closely related plant species and shows the same specificity as the Indian isolate. Potentially, both strains could be released to control the plant.
Sources
Varia S, Pollard K, Ellison C (2016) Implementing a novel weed management approach for Himalayan balsam: progress on the biological control in the UK. Outlooks on Pest Management 27(5) 198-203.