Associate Professor Oregon State University Aurora, Oregon
Worldwide, aphid pest pressure can be impactful in hazelnut (Corylus avellana L.) production, resulting in defoliation, poor kernel quality, and the growth of sooty mold. The Corylus aphid complex is comprised of the hazelnut aphid, Corylobium avellanae (Schrank) and filbert aphid, Myzocallis coryli (Goetze) (Hemiptera: Aphididae). These species occupy distinct niches; the filbert aphid feeds predominantly on the underside of leaves at the production source of photosynthates and carbohydrates, while the hazelnut aphid is the predominant species on the trichomatous husks, the seasonal carbohydrate sink. In Oregon, the filbert aphid has a history of resistance to insecticides, as well as a history of classical biological control, yet the current action thresholds were developed prior to the introduction of hazelnut aphids (circa 2005). Critically, damage from the two species may be synergistic. These challenges highlight the need for novel, non-chemical management strategies for sustainable production. Here, three EPF isolates, Metarhizium brunneum (Hypocreales: Clavicipitaceae), Cordyceps spp., and Beauveria bassiana (Hypocreales: Cordycipitaceae), were tested for acute and sublethal effects on filbert and hazelnut aphid populations. Spray trials assessed mortality rates in mature aphids over seven-day periods. While soil drench applications, tree injections, and foliar applications to tissue cultured trees were used to track endophytic persistence, as well as the effects on aphid parthenogenesis and mortality over the course of the growing season.