Effects of temperature and exposure time on mortality of stored-product insects exposed to low pressure

The prospects of using low pressure that creates a low-oxygen atmosphere to control stored-product insects were investigated in the laboratory. Eggs, larvae, and pupae of Tribolium castaneum (Herbst), Plodia interpunctella (Hubner), and Rhyzopertha dominica (F.) were exposed to 32.5 mmHg in glass chambers at 25, 33, 37, and 40 degreesC for times ranging from 30 min to 144 h. Time-mortality data were subjected to probit analyses and lethal dose ratios were computed to determine differences in lethal time (IT) values among all species-life stage combinations across the four temperatures, Eggs of each species were the life stage most tolerant to low pressure. Pupae of T. castaneum and R dominica were more tolerant to low pressure than larvae. in all life stages, mortality increased with increasing exposure time to low pressure and also with increasing temperature. Immature stages of R. dominica were more tolerant to low pressure than immature stages of the other two species, The LT99 for R. dominica eggs was 176.32 h at 25 degreesC and that for F. interpunctella eggs was 28.35 h at the same temperature. An increase in temperature to 33 degreesC resulted in a LT99 of 85.98 h for R. dominica and 6.21 h for F. interpunctella. Higher temperatures resulted in further significant reduction in lethal time values. Low pressure represents a simple, nonchemical alternative to fumigants such as methyl bromide and phosphine for controlling pests of stored-products or other commodities.