Factors Affecting the Efficacy of Deladenus siricidicola in Biological Control Systems

The nematode, Deladenus (=Beddingia) siricidicola, represents the cornerstone of Sirex noctilio biological control programs across the Southern Hemisphere. There is, however, significant variation in its efficacy in different regions. In this review, we consider emerging issues related to the biology and handling of the nematode that might influence its efficacy in biological control systems. Most practical aspects concerning the handling of D. siricidicola have been streamlined over the past half-century and these appear to be very efficient. However, large gaps remain in our knowledge about some key aspects of the biology of D. siricidicola. For example, very little is known regarding the evolution of virulence in the nematode populations, and the consequent evolution of resistance in S. noctilio populations. Furthermore, the levels of diversity in D. siricidicola and its ability to adapt to fungal, wasp and environmental variation are poorly understood. In this regard, new collections and storage of native populations of the Deladenus spp. are critical for the future research and management of this key biological control agent of S. noctilio.