A review of the history of the biological control agents introduced to combat weeds has found that some have produced incredible results.
Others, however, were next to useless.
Max Suckling is science group leader of biosecurity at Plant and Food Research and his latest work has taken a look at the benefits of biological control introduction.
He says the success rate of different controls has varied greatly, but two massively successful ones have both had a big impact on farms.
He says the St John's wort beetle has helped take out St John's wort, which is poisonous to stock,
and the ragwort flea beetle has fought the invasive ragwort, which damages the livers of cattle and horses.
Dr Suckling says if people are interested in finding out more about the science and history behind biological control introductions in New Zealand they should visit the website www.b3nz.org and go to the links page.