Enhanced effectiveness of vacuum or CO2 in combination with increased temperatures for control of storage insects.

Abstract

AbstractLaboratory studies were conducted to determine the combinations that enhance the effectiveness of insect control based on vacuum or CO2 in combination with increased temperatures as quarantine treatment of storage pests. The effects of commodity (cocoa beans) moisture content and the partial pressure of oxygen on the effectiveness of vacuum were studied. For Tribolium castaneum, Ephestia cautella [Cadra cautella] and Plodia interpunctella, the egg stage was the most resistant to low pressure: the duration required to obtain LT99 was 22, 45 and 49 h, respectively. For Tribolium castaneum, the larval and adult stages were the most susceptible, with an LT99 of 7 h. For E. cautella and P. interpunctella, the adult stage was the most susceptible, with LT99 of only 6 and 5 h, respectively. The evaluation of the effect of CO2 at 45°C on the reduction of exposure time for diapausing larvae of T. granarium indicated that by increasing the CO2 concentration to 90%, the LT99 value was reduced to approximately 10 h (LT99 value of 29 h at 35°C). For E. cautella, the larval stage was the most resistant to 90% CO2 at 40°C, with an LT99 value of only 6 h. For O. surinamensis under the same conditions, the LT99 value was 9 h for the most resistant egg stage. A transportable flexible storage system was developed for the control of insect pests. Experiments were carried out using a 15 m3 capacity plastic container termed the "Volcani Cube" or "GrainPro Cocoon". Bioassays in field trials [location not given] at 30°C demonstrated that complete mortality of test insects representing all the four developmental stages of E. cautella and Tribolium castaneum was observed upon three-day exposure to vacuum maintained between 23 and 75 mm Hg.