Reevaluating filbertworm (Cydia latiferreana) phenology: Implications for management in Willamette Valley orchards

The Filbertworm (FBW), Cydia latiferreana (Walsingham) (Lepidoptera: Tortricidae), is the key pest of hazelnuts in Oregon’s Willamette Valley, where 99% of the US crop is grown on roughly 95,000 acres. Adult female FBW moths lay individual eggs on leaves, close to the developing nut clusters. Once the eggs hatch, the larvae search out nut clusters. Once on the nut, larvae chew a small entry hole through the micropyle, a small pore on the basal scar of the shell, they begin feeding on the kernels. Low tolerance for damage (>1%) necessitates spray treatments against the pest. Untreated orchards are seen to experience upwards of 50% infestation rates. While there is a simple degree-day model to guide management timing, our data suggests that it is not performing well, and it also does not predict life stage events after the initial flight period and coinciding egg laying and egg hatch period. Moth flights appear to be occurring both earlier and later in the season than historic norms, and growers particularly need guidance on late-season management. Most growers rely on a trap threshold method to time sprays, though some still use a calendar-based approach. This research aims to gain a more robust understanding of the FBW and its damage by examining the viability of the FBW degree-day model, suggesting improvements using flight data from a large smart trap network throughout the Willamette Valley, intensive field sampling for immature stages, and lab-based temperature-dependent development studies to reevaluate the temperature thresholds.