Search for baculoviruses in sawflies (Hymenoptera: Diprionidae) in Mexico

Introduction: Sawflies (Hymenoptera: Diprionidae) affect conifers and other forest species in the northern hemisphere, reducing forest productivity and causing stand death, thereby justifying control actions.Objective: The aim was to collect baculoviral strains from Mexican sawfly populations and explore their potential for developing biopesticides.Materials and methods: A search for baculovirus-infected field populations was carried out. Twenty-three samples of live or dead larvae were collected from 12 localities. Microscopic diagnosis at 400X or 1000X under phase contrast, a DNA hybridization test, and a pathogenicity test were performed.Results and discussion: Samples from eleven localities showed baculoviral polyhedra. Three subsamples of Zadiprion ojedae DNA from Guachochi, Chihuahua, hybridized with a synthetic probe of the Neodiprion sertifer Polh gene sequence, confirming they harbored baculovirus infection.Five tested inocula produced disease and mortality in all treated larvae; two of them induced baculoviral polyhedra proliferation in ≥ 89 % of the resulting cadavers. The rictus mortem of sawfly larvae killed by baculovirus differs from that observed in Lepidoptera: most baculovirus-bearing cadavers remain firm or hard, flattened or not, obscured or not, and do not hang from the hind legs. For most of the cadavers found with liquefied tissues, the agent that most probably caused death was not the baculovirus but the accompanying microbiota (bacilli, cocci, or fungi).Conclusions: Baculovirus strains are widely present in Mexican sawfly populations and several of them were pathogenic and promising for developing bioinsecticides.