GROUND COVER AND PREDATORY ARTHROPODS IN WASHINGTON SWEET CHERRY ORCHARDS

Peter R. Smytheman

doi:10.7273/000007244

Tree fruits, including apples, pears, cherries, and other stone fruits, are economically important crops grown in temperate regions worldwide. These crops are vulnerable to various pests and vector-borne diseases that reduce productivity and profitability, leading to reliance on chemical controls. Some pests affect multiple tree fruit species, and their management is crucial for sustainable orchard production. Epigeic (living on or near soil surface) predatory arthropods, such as carabid beetles, harvestmen, centipedes, and spiders, are natural enemies that inhabit the orchard floor and play a vital role in pest suppression by preying on a range of species. This research identifies the epigeic predator taxa present in Washington State cherry orchards, and how ground cover management strategies may impact them. In 2023, I conducted a survey across 13 sweet cherry orchards over a 300 km region of Washington State east of the Cascade mountains. Five of the orchards were certified organically managed, and eight were conventionally managed. Using pitfall traps, I sampled the epigeic predator community weekly from late April to early August, then at reduced frequency until September. The most abundant predators found were carabid beetles, harvestmen, centipedes, and spiders, all potential biological control agents of pests like spotted-wing drosophila, western cherry fruit fly, and leafhoppers, whose immature life stages occur in the soil or groundcover for a period of time ranging from days to months. The second study assessed the effects of a reflective geotextile (Extenday®) on epigeic predator activity densities in post-harvest cherry orchards. In 2021 and 2022, pitfall traps compared predator activity densities in geotextile-treated, kaolin clay-treated (2021), herbicide-treated (2022), and untreated control plots. In 2021, significantly more carabid beetles and centipedes, but fewer harvestmen, were found in the geotextile-treated plots. In 2022, fewer harvestmen and spiders were observed in the geotextile-treated plots, but carabid beetle and centipede numbers showed no significant difference from the controls. These findings suggest that reflective geotextiles may alter the groundcover environment, influencing predator composition and activity. Understanding these interactions can improve biological control integration and enhance sustainable pest management strategies in cherry orchards.

GROUND COVER AND PREDATORY ARTHROPODS IN WASHINGTON SWEET CHERRY ORCHARDS

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