Susceptibility of dried berries to infestation by Plodia interpunctella (Lepidoptera: Pyralidae) in correlation with total sugar content

By assessing the degree of resistance of stored products to infestation by insect pests and correlating it with physical, chemical and nutritional characteristics of products, we could gain a real insight in these pests feeding preferences, and consequently in their biology and ecology. The aim of this study was to assess the degree of resistance of five dried berry species (strawberry, raspberry, blackberry, black chokeberry and cranberry) to infestation caused by the major pest of dried berries, Plodia interpunctella. Susceptibility was rated based on the Index of susceptibility (IS) for insect development and the Susceptibility rating. Dried cranberries were absolutely resistant to infestation by P. interpunctella (IS = 0) - no larvae reached the adult stage. Four other dried berry species were also resistant (IS ranged 2.01 – 2.44). In other words, dried cranberries are very unsuitable food for P. interpunctella, while other four tested species were slightly more suitable. The content of total sugars in dried berries varied from 24.2% (black chokeberry) to 72.8% (strawberry), but important correlation between IS and total sugar content was not found. By analysing feeding preferences of P. interpunctella, we can undertake different pest-management strategies for protection of stored dried fruits.