SirexWoodwasp: A Model for Evolving Management Paradigms of Invasive Forest Pests

Abstract

The Sirex woodwasp, Sirex noctilio, and its fungal mutualist, Amylostereum areolatum, together constitute one of the most damaging invasive pests of pine. Despite a century of research and well-established management programs, control remains unpredictable and spread continues to new areas. Variable success in managing this pest has been influenced by complex invasion patterns, the multilayered nature of biological interactions, the varying local ecologies, and microevolutionary population processes in both the biocontrol organisms and in the wasps. Recent research findings are challenging the historical perspectives on methods to manage the Sirex woodwasp, calling for management programs to incorporate the variable local dynamics affecting this pest complex. In this regard, the Sirex woodwasp provides a superb model to illustrate the need for a different approach to develop efficient and sustainable management tools to deal with the growing and global nature of pest invasions in forests and plantations.

Comparing functional traits and abundance of invasive versus native woodwasps

“…Sirex noctilio is not a pest where it is native in Eurasia and North Africa, but has caused economic damage in plantations of exotic pines (Pinus spp.) after introductions in the southern hemisphere (Slippers et al 2015). Established populations of S. noctilio were first reported in northeastern North America in 2004 (Hoebeke et al 2005) and this invasive now occurs in eight eastern US states (CERIS 2017) and two eastern Canadian provinces (de Groot et al 2006, CFIA 2009 and it is expected to continue to spread.…”

Performance of Sirex noctilio ’s biocontrol agent Deladenus siricidicola , in known and predicted hosts

“…Breeding pines for resistance to Sirex has not been a focus of management because of the success of existing management strategies (Slippers et al, 2015), but it is possible that germplasm could be selected that would promote nematode survival. Further work in identifying these factors is warranted.…”

“…The freeliving form is thus spread naturally when infected S. noctilio females lay packets of nematodes in place of viable eggs into trees, and operationally by inoculating laboratory-cultured nematodes into felled trees. The success of the biological control program is influenced by interactions between wasp, nematodes and fungal strains (Morris et al, 2012;Slippers et al, 2015), other insects and fungi (Yousuf et al, 2014), climatic conditions (Hurley et al, 2007) and host tree characteristics (Bedding, 2009).…”

Host specificity and diversity of Amylostereum associated with Japanese siricids

“…Slippers et al (2015) suggest that wasps could acquire sexually produced genotypes of the fungus, which could help explain the higher VCG diversity observed in North America.…”

“…The siricid-Amylostereum mutualism is maintained across wasp generations by transmission of asexually produced propagules of the fungus by the female wasp 2015). Female siricid wasps have specialized internal organs called mycangia in which they carry asexual arthrospores of Amylostereum which they introduce into the tree host whilst laying their eggs.…”