Losses of walnut, almond and hazelnut kernels as a result of Plodia interpunctella larval feeding

Abstract: Plodia interpunctella is regularly present in stores and warehouses of dried and stone fruits throughout Serbia. The aim of this study was to determine the amount of consumed food during larval developmental of P. interpunctella, reared on broken kernels of walnut (Juglans regia), hazelnut (Corylus avellana) and almonds (Amygdalus communis). The experiment was set up in three series (walnut, almond, hazelnut) with 12 jars in each series. Each jar contained 100 ml of culture medium. The amount of consumed food during the larval development was measured on the first (initial) and the second (final) observation. The biggest consumption is registered on hazelnut – 3.85 g (8.29%), walnut – 3.31 g (6.91%) and almond 3.13 g (5.95%) in jars with 29, 25 and 35 larvae, respectively. The lowest kernel consumption was on almonds – 1.28 g (2.42%), hazelnut – 1.32 g (2.98%) and walnut – 1.73 g (2.75%) in jars with 20, 6 and 12 larvae, respectively. On almonds with the lowest number of larvae (19), the registered reduction in kernels weight was 4.24% (2.25 g). The average value of the consumed food per jar was 2.64 g on hazelnuts, 2.35 g on almonds and 2.22 g on walnuts. The average weight of consumed food per larvae was 0.08 g on almonds, 0.09 g on walnuts and 0.13 g on hazelnut. It can be concluded that the larvae are “poor” consumers of available food. The number of developed larvae statistically significantly differed among substrates. The biggest was on almonds (344), followed by walnut (285) and hazelnut (235). Direct damages are therefore negligible, but the indirect damages, that are visible as worm holes and the presence of larvae and moths, are reducing market value of these fruit products.