DEVELOPMENTAL THRESHOLDS AND DEGREE-DAY ACCUMULATIONS OF INDIANMEAL MOTH (LEPIDOPTERA, PYRALIDAE) ON DRIED FRUITS AND NUTS

Degree-days for egg to adult development were determined for a laboratory and a wild-type isolate of the Indianmeal moth, Plodia interpunctella (Hubner), reared on wheat bran diet, almonds, pistachios, walnuts, raisins, and prunes. To avoid problems with temperature-induced diapause and effects of diet, eggs and pupae were used to estimate developmental thresholds used in degree-day determinations. Lower developmental thresholds for eggs (14.8 degrees C) and pupae (13.8 degrees C) of both isolates were identical. A threshold of 14 degrees C was used for degree-day determinations for both isolates. Egg hatch on all diets was lower for the wild-type isolate, but postembryonic survival of the wild-type isolate was similar to the laboratory isolate. Survival was <12% on dried fruits, 76.5-91.7% on nuts, and 95.3-97.3% on wheat bran. Degree-days for the laboratory isolate for each diet was lower than those for the highest when reared on dried fruits. The determination of development thresholds for eggs and pupae allows the use of a single lower threshold for all models, although different degree-days will be necessary for each commodity.