In this section
Once established, biocontrol is inexpensive compared to other control methods
Unlike herbicides, which need to be reapplied regularly to control weeds, a well-established biocontrol agent can do its job with little input from people. Successful biological control for mist flower, St. John’s wort, and ragwort means that it is rare for other control methods to be required for these weeds. So in the long term, biocontrol can be very cheap.
Some weeds can’t be controlled by conventional methods
Some weeds are difficult to kill with herbicides, and quickly resprout from roots or seeds after herbicide application. Other weeds are so widespread or found in such inaccessible areas that using herbicides is not economically feasible. Biocontrol agents can penetrate even the most inaccessible and widespread weed populations, and they keep coming back as the weed resprouts.
Biocontrol can be more environmentally friendly than conventional methods
Some weeds invade sensitive or rare native habitats, where herbicides would kill important native flora and fauna. Biocontrol agents eat only weeds, leaving desirable plants untouched, and they don’t pollute the soil or waterways.
Heather: The making of a weed
History of heather in New Zealand. Originally sowed and planted by John Cullen in Tongario National Park as a habitat for gamebirds. Grouse was introduced but did not survive in New Zealand. However heather has established and is a major problem in the park, forming dense mats, displacing natural vegetation and the homes of native invertebrates and lizards. For nearly 100 years efforts have been made to eradicate heather without much success.