Evaluating low temperatures to control Indian meal moth in stored grain

Aeration management strategies were developed to control cold-acclimated and diapausing Indian meal moth larvae in grain bins in north- and east-central regions of the U.S during winter. Contour maps showing hours below -10°C for the months of December, January, and February were developed to help effective planning and management of aeration to control insects that normally survive the winter. Two cumulative lethality index (CLI) models were developed to estimate mortality of laboratory-reared (diapausing without cold-acclimation) and field-collected (cold-acclimated, and diapausing with cold-acclimation) Indian meal moth larvae under changing temperature conditions. The CLI models were found to be useful for evaluating aeration management strategies. Simulation studies were conducted using 30 years of weather data for twelve locations in north- and east-central regions of the U.S. to evaluate different aeration management strategies for controlling Indian meal moth larvae. Temperatures of headspace-air and grain in the top meter of grain were simulated using an existing model for the period of December to February. The tested management strategies included no aeration, continuous aeration, and intermittent aeration by controlling fan operation. During aeration, air was pulled from the headspace downward through the grain (downward airflow). Among the tested management strategies, a fan control strategy that turned the aeration fan on when the temperature of grain at 0.4 m depth was greater than the headspace-air temperature was found to be the best aeration management strategy for managing Indian meal moth larvae in all tested locations. For this strategy, the CLI model indicated that 100% mortality of Indian meal moth larvae could be achieved at a grain depth of 0.4 m from the top grain surface in all locations. For this strategy, the aeration fan operated about 10% of the time from December to February. The average cost of electrical energy required for aeration fan operation with this strategy for all locations was 1.3 ¢/t (0.03 ¢/bu) based on an electrical energy cost of 7 ¢/kWh.