The Sirex Woodwasp in New Zealand: History and Current Status

The European woodwasp, Sirex noctilio, was first found in New Zealand in 1900, but was not recognized as a pest until the late 1920s after deaths of pines in overcrowded plantations were attributed to it. Despite the successful introduction of a parasitoid from Europe as a control measure, damage became more prevalent between 1946 and 1951 when extreme drought conditions confounded the problem. This led to investigation of other parasitoids, some of which were also successfully introduced. In addition, a nematode causing female sterility, discovered to have been introduced along with S. noctilio, was effectively propagated and disseminated. To date, both biological control agents and silvicultural methods have caused a significant decrease in S. noctilio populations so that it is now rare in plantations and considered to be a minor pest.