Safety in New Zealand weed biocontrol a nationwide pathogen survey for impacts on nontarget plants

Abstract

The accuracy of host range testing in weed biocontrol programmes using plant pathogens has been questioned prompting a research programme into the field safety record of pathogens used for weed biocontrol in New Zealand Nationwide disease surveys were conducted from 20002009 and focused on species closely related to target weeds and therefore potentially most at risk of attack These surveys identified pathogens associated with any disease symptoms observed on nontarget hosts Disease damage attributable to biocontrol agents was observed on two nontarget plants Pustules of the blackberry rust Phragmidium violaceum were found on the endemic Rubus species R cissoides (bush lawyer tataramoa) at one location This result was predicted from host range safety tests conducted prior to its arrival in New Zealand No nontarget damage was observed in the remaining case studies confirming to date that all biocontrol pathogens are highly host specific to their target weeds