Effect of low temperatures on the rate of respiration and uptake of phosphine in different life stages of the cigarette beetle Lasioderma serricorne (F.)

Studies were undertaken to establish the effects of low temperatures on the rate of respiration in larvae and adults of a susceptible strain of the cigarette beetle Lasioderma serricorne. The results showed that there was a consistent decrease in the rate of respiration in L. serricorne with a decrease in temperature from 25°C to 5°C. The rate of respiration was slightly affected by circadian rhythm in adult beetles, but not in larvae.The levels of phosphine taken up by different life stages of the beetle were also determined using ³²P]-radiolabelled gas. A comparison between susceptible and phosphine resistant strains showed that the mechanism of resistance in L. serricorne involves a reduced uptake of the fumigant.The uptake of ³²P]-phosphine by different life stages of resistant L. serricorne declined with a decrease in temperature from 25°C to 5°C. Similarly, the uptake by susceptible L. serricorne decreased from 25°C to 10°C, but there was a comparatively higher uptake at 5°C and consequently a higher mortality at the end of the exposure. The significance of the findings in relation to control strategies is discussed.