Exploring natural allies: identifying larval parasitoids for sustainable management of grape berry moth in vineyards

Grape berry moth (GBM), Paralobesia viteana is the most important pest of grapes in the Northeast US. The larvae of this pest damage grapes by direct feeding and increasing susceptibility to fungal pathogens. Current pest management relies heavily on pesticide applications, posing environmental and health risks. Yet, this conventional approach is not totally effective against GBM larvae, which can evade pesticides by burrowing into fruit upon hatching. This study explores the potential of utilizing natural enemies, specifically larval parasitoids, as a sustainable alternative to traditional pesticide-based GBM management. We sampled six vineyards in Erie County, Northwest Pennsylvania, throughout the 2023 growing season. Grape samples showing signs of GBM infestation were collected and kept in laboratory conditions. These samples were monitored daily to track the emergence of both parasitoids and GBM. GBM parasitism rates were calculated using the number of parasitoids that emerged divided by the sum of parasitoids and moths that emerged multiplied by 100. Results revealed varying parasitism rates across different sites and sampling dates, ranging from 3.4% to 21.7%. A total of six distinct parasitoids were identified, representing at least four different genera, with Bracon variabilis and Enythus sp being the most abundant. While full identification of the parasitoids is underway, our research highlights the presence of diverse larval parasitoids of GBM in Northwestern Pennsylvania. These findings represent a great opportunity for the use of larval parasitoids in GBM control programs, hence the need to study them further.