Toxicity of conifer needle endophytes to spruce budworm

The production of metabolites which are toxic to the spruce budworm by endophytic fungi in balsam fir and red spruce needles was investigated. From a collection of ca 900, 94 strains were selected at random and grown in liquid culture. Five strains produced extractable compounds that resulted in mortality and/or a reduced rate of development in spruce budworm larvae. Three of the strains produced potent toxins. These data could explain unresolved mortalities of the spruce budworm in New Brunswick. Cultured spruce budworm cells proved to be a useful bioassay for the identification of strains producing toxins to larvae.