Persistence of conidia and potential efficacy of Beauveria bassiana against pinhole borers in New Zealand southern beech forests

Three native species of pinhole borer Treptoplatypus caviceps, Platypus apicalis and Platypus gracilis (Curculionidae: Platypodinae) are occasional pests of indigenous forests in New Zealand. These species predominantly attack ‘southern beech’, usually colonising fallen logs or stumps, but populations can reach densities which threaten healthy trees when large amounts of breeding material are available. The larvae live in tunnels which penetrate deep into the trees. Few control processes or agents are known in New Zealand. A search for naturally occurring biological enemies of pinhole borer resulted in the isolation of several insect-pathogenic fungi, the majority of isolates being Beauveria bassiana. Several strains of B. bassiana were isolated from pinhole borer in South Island southern beech forests, as determined by sequencing of the ITS-5.8s region of rDNA.