Enhanced effectiveness of vacuum or CO_2 in combination with increased temperatures for control of storage insects

摘要

Laboratory studies were carried out to identify the combinations that enhance the effectiveness of insect control based on vacuum or CO_2 in combination with increased temperatures, as a quarantine treatment of storage pests. The effects of the commodity moisture content and the partial pressure of oxygen on the effectiveness of vacuum were described. For T. cstlaneum, E. cautella and P. interpunctella the egg stage was the most resistant to low pressure: the times needed to obtain LT_(99) were 22,45 and 49 h, respectively. For T. castaneum the larva and adults were the most susceptible stages with an LT_(99) of 7 h. For E. cautella and P. interpunctella the adult was the most susceptible stage with LT_(99) times of only 6 h and 5 h. The effect of CO_2 at 45 deg C on reducing the exposure time for diapausing larvae of T. granarium showed that by increasing the CO_2 concentration to 90 percent the LT_(99) value was reduced to about 10 h, whereas at 35 deg C the LT_(99) value was 29 h. in Ephestiacautella larvae were shown to be the most resistant stage to 90 percent CO_2 at 40 deg C, with an LT_(99) value of only 6 h. For Oryzaephilus surinamensis under the same conditions, the LT_(99) value was 9 h for the most resistant egg stage. These encouraging results led to the idea of developing a transportable flexible storage system to render the technology a practical tool for the control of insect pests. Experiments were carried out using a 15 m~3 capacity plastic container termed the "Volcani Cube~(TM)" or "GrainPro Cocoon~(TM)", Bioassays in field trials at 30 deg C demonstrated that complete mortality of test insects representing all four developmental stages of E. cautella and Tribolium castaneum was observed upon three days exposure to vacuum maintained between 23 and 75 mm Hg.