Exploring artificial diets for the laboratory rearing of Sirex noctilio late-instar larvae: a qualitative study

Sirex noctilio (Hymenoptera: Siricidae) is a well-known pest in commercial pine plantations in the Southern Hemisphere. It is difficult to study the development of the woodwasp since it spends most of its life inside the host tree. Researchers have developed extraction methods, such as splitting logs or sawing thin sections of a log, to examine internal parts of the host tree and study S. noctilio, but these methods are labour-intensive and time-consuming. Artificial diets have been developed for many insects allowing researchers to observe all life stages of an insect, as well as to enable broader experimentation with these life stages. The aim of this study was therefore to initiate the development of an artificial diet for S. noctilio larvae and to evaluate the suitability of this diet for the laboratory rearing of S. noctilio. Three artificial diets were qualitatively tested for the rearing of S. noctilio late-instar larvae, which included (A) modified versions of a commercially produced Anoplophora glabripennis (Coleoptera: Cerambycidae) diet, (B) agar-based pine shavings/sawdust diet, and (C) wheat/rice diet used to rear Deladenus siricidicola (Tylenchida: Neotylenchidae). In addition, different techniques for rearing larvae on the artificial diets were evaluated. The results showed that the original A. glabripennis diet, including some modified versions, worked the best to rear S. noctilio larvae. Compared to other methods, rearing larvae inside Petri dishes was most suitable. The method developed in this study shows potential to reduce labour and space for conducting research on S. noctilio, and forms the basis for the establishment of a laboratory reared population.