Release of Psychophagus omnivorus (Walker, 1835) (Hymenoptera: Pteromalidae) against Hyphantria cunea (Drury, 1773) (Lepidoptera: Erebidae) in hazelnut orchards

The fall webworm, Hyphantria cunea (Drury, 1773) (Lepidoptera: Erebidae), is a highly polyphagous and destructive pest that damages a wide range of host plants in agricultural, urban and forest areas. It occasionally poses a major threat to hazelnut cultivation, including Türkiye. This study evaluated the field performance of the pupal parasitoid Psychophagus omnivorus (Walker, 1835) (Hymenoptera: Pteromalidae) against H. cunea in heavily infested hazelnut orchards in Düzce, Türkiyebetween 2020 and 2021. A two-year study was conducted using a randomized complete block design with four replications to evaluate the parasitism rates of H. cunea by P. omnivorus in two generations. Psychophagus omnivorus releases had a significant impact on pupal parasitism rates, with this effect varying significantly between generations and across the two years. In 2020, parasitism rates in parasitoid-release plots reached 67.6% and 78.9% in the first and second generations, respectively, while control plots showed 0% and 13.9%. In 2021, parasitism reached 63.3% and 76.5% in parasitoid-release plots, compared to 0% and 45.4% in controls. These findings demonstrate the high potential of P. omnivorus as a biocontrol agent for the sustainable management of H. cunea in hazelnut orchards.