Two species of aphids, the filbert aphid Myzocallis coryli (Goetze) (Hemiptera: Aphididae), and the hazelnut aphid Corylobium avellanae (Shrank) (Hemiptera: Aphididae), are pervasive and abundant pests of Oregon’s hazelnut cropping system. The filbert aphid feeds predominantly on the abaxial surface of leaves and is noted for extracting nutrient rich exudates from the plants photosynthetic source. Alternatively, the hazelnut aphid feeds on developing nut clusters, peduncles, and petioles, and extracts resources from the tree’s nutrient sink. This synergistic seizure of requisite nutrients by both species is known to reduce kernel fill, cause irreversible damage to discrete plant tissues, and cause premature leaf drop, while excess waste produced by the aphids additionally facilitates the growth of black sooty mold (Pacific Northwest Pest Management Handbooks, 2015). Though conventional chemical treatments paired with classical biological control efforts have successfully mediated aphid damage in the past, recent constraints imposed by invasive pests and developing pathogens have incentivized research into biological alternatives that alleviate synthetic chemical dependency. Entomopathogenic fungi are notorious insect pathogens known to cause epizootics and prolonged population control in several aphid species (Saussure et al., 2024), while simultaneously inducing sublethal effects, such as reduced fecundity (Fingu-Mabola et al., 2021). Here, we evaluate the lethal and sublethal pathogenicity of three entomopathogenic fungal isolates, Metarhizium brunneum, Beauveria bassiana, and Cordyceps, and one field isolate, against mature filbert and hazelnut aphids. Results indicate that while all four fungal species inact effective control, Metarhizium brunneum and Beauveria bassiana induce the highest mortality rates combined with reduced fecundity.
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