Biomedical Engineering Reference
In-Depth Information
Similar results were obtained with pupae of these two species. The exposure of
larvae, pupae, and adults of
O
.
surinamensis
to 77% CO
2
at a relative humidity of
50% and temperatures ranging from 16 to 32°C showed that the pupae were more
tolerant than either adults or larvae. The exposure time to obtain 100% mortality
decreased with an increase in temperature. In another study, various developmental
stages of
Trogoderma granarium
Everts were subjected to controlled atmospheres
containing 60% CO
2
in air at 20 or 30°C and a relative humidity of 60%.
66
Although
the eggs, pupae, and adults all died within 6 days of exposure, some larvae survived
even after 16 days. Further exposure of larvae to 45, 60, and 75% CO
2
in air indicated
that an exposure of >15 days to 75% CO
2
at 30°C is required for 100% mortality
of larvae of this species.
The importance of relative humidity in the control of stored-product insects with
controlled atmospheres was studied by Jay et al.
67
The adults of
T
.
castaneum
,
T
.
confusum
, and
O
.
surinamensis
were exposed to binary mixtures of O
2
and N
2
(<1% O
2
: >99% N
2
), and ternary mixtures of O
2
, N
2
, and CO
2
(9.8% O
2
: 30.5% N
2
:
59% CO
2
or 13.1% O
2
: 49.3% N
2
: 37.6% CO
2
) at four different relative humidities
(7 to 9, 30 to 33, 53 to 60, or 68 to 73%). The mortality of insects increased
significantly with a decrease in relative humidity under all gas compositions. Navarro
and Calderon
68
studied the effect of relative humidity (20 to 22, 54 to 55, and 95 to
96%) on the mortality and weight loss of 0- to 24-h-old pupae of
Ephestia cautella
(Wlk.) under various concentrations of CO
2
(0, 21, 51, 88%) at 26°C. The pupal
mortality was high at low relative humidity (<55%) at all CO
2
concentrations. At
high relative humidity (95%), however, complete mortality was obtained only when
the CO
2
concentration was 88%. After 6 days of exposure, the pupal weight loss
was high (45 to 55%) at low relative humidity (<55%) but minimal (<16%) at high
relative humidity (95%). Therefore, the pupal mortality may be attributed to the loss
of water at the low relative humidity. Spratt
69
investigated the productivity of
T
.
castaneum
and
T
.
confusum
in an atmosphere containing 5 to 20% O
2
with or
without 10% CO
2
. The relative humidity (70%) and temperature (30°C) were kept
nearly constant. The egg production was about 60% higher in the presence of CO
2
at O
2
concentrations of 5.0, 7.5, and 10.0%. No difference in egg production,
however, was observed in the presence or absence of CO
2
at 21% O
2
. Egg hatch
was seriously impaired at 5% O
2
with or without CO
2
. No significant adult mortality
was observed in any of the gas conditions and in all cases the normal fecundity was
regained when normal gas atmosphere was restored.
White et al.
70
observed the effects of CO
2
concentrations and temperature on
adult survival and reproduction of beetle
C. ferrugineus
, and determined that fumi-
gation of grain for 1 week at 20°C would require 94% CO
2
and <1% O
2
. White
et al.
71
exposed all life stages of
C. ferrugineus
to different concentrations of CO
2
at 25 ± 3°C or at temperatures declining from 21 to 7°C. Insects were controlled in
4 to 6 weeks at 25 ± 3°C when CO
2
levels were approximately 20% and O
2
levels
were between 5 and 10%. At temperatures declining from 21 to 7°C, 99.6% of
C. ferrugineus
populations were killed in 12 weeks, when CO
2
levels gradually fell
from 20 to 9% and O
2
levels rose from 16 to 19.5%. Further tests indicated that
four CO
2
purges between 15 and 50% on weeks 0, 1, 2, and 4 in bins with 6-day
half-lives for CO
2
loss virtually eliminated insect and mite pests in 42 days at 12 to
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