The effect of controlled atmospheres (CAs) of 30 and 60% CO2 or
99.9% N2 at various temperatures (15, 20, 25, 30 or 35°C) and 60*5% R.H. was
investigated on all developmentaj stages of Triboleum castaneum (Herbst) and
active or diapausing larvae of Trogoderma granarium Everts). For Triboleum
castaneum the egg stage was the most sensitive to CO2 at all tested temperatures.
LT99s reduced from 3.8 days at 15°C to 2.8 days at 35°C under 30% CO2 and
from 3.2 days at 15°C to 2.5 days at 35°C under 60% CO2. The susceptibility of
pupal stage occupied the second range after the egg stage at all tested
temperatures and CO2 concentrations. The larval stage was the least sensitive to
30% CO2 at all tested temperatures and at 25, 30, 35°C to 60% CO2 (LTs
shortened from 16.6 days at 15°C to 5 days at 35°C under 30% CO2 and to 3.1
days at 35°C under 60% CO2). The adult stage was only the least sensitive to 60%
CO2 at 15°C and 20°C (LTs decreased from 7.1 days at 15°C to 5.6 days at
20°C). Under CA of 99.9% N2 the larval and adult stages were the most sensitive
at 15 to 30°C while the pupal and egg stages were the least sensitive.
For Trogoderma granarium, the active larvae were more susceptible
than the diapausing larvae only when exposed to 60% CO2 at all tested
temperatures and 99.9% N2 at 35°C. LTs of active larvae decreased from 20.1
days at 15°C to 7.9 days at 35 °C under 60% CO2 and to 9.2 days at 35 °C under
99.9% N2, LT99s of diapausing larvae decreased from 43.4 days at 20°C to 9.1
days at 35°C under 60% CO2 and to 12.1 days at 35°C under 99.9% N2.
It was concluded that 60% CO2 was most effective and the temperature
dependence of the insect sensitivity to gases was noticeable at every stage. At the
highest tested temperature (35 °C), slight mortality variation among the
developmental stages of Tri boleurn caslaneurn or active and diapausing larvae of
Trogodermcz granariurn was observed.
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