First Report of Amylostereum spp. Association With the Woodwasp Sirex obesus Bradley (Hymenoptera: Siricidae) in Brazil

Woodwasps of the genus Sirex are known to have an obligatory symbiotic relationship with Amylostereum fungi. During oviposition, these wasps inoculate arthrospores of the fungus along with a toxic mucous secretion. As a result, attacked conifer trees can exhibit symptoms of decline and death. The aim of this study was to evaluate the diversity of Amylostereum fungi associated with Sirex obesus . To achieve this, female S. obesus wasps were collected from Pinus plantations in Brazil. The mycangia were removed from the wasps using a stereoscope under aseptic conditions. These structures were subsequently macerated in sterile 0.85% saline solution, and aliquots of the resulting suspension were plated onto PDA medium. Fungal growth was monitored daily, and the colonies were purified and identified by sequencing the ITS‐rRNA gene region. As a result, we observed that Amylostereum chailletii and Amylostereum areolatum were present in the mycangia of the dissected wasps, with A. chailletii occurring more frequently (93.3%). The association between A. areolatum and S. obesus still requires further study. This discovery has direct implications for the control of this species of wood wasp and may serve as a basis for future research aimed at developing management strategies.