الفهرس 
Material and methodsOnly 14 pages are availabe for public view
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Abstract
The objective of this work was to investigate the
efficiency of phosphine, carbon dioxide alone and their
mixtures against some important insect species causing
damage to stored cereal grains and pulses in Egypt, namely:-
E...:.. oryzae (L.), .!h dominica (F.) and.£.:. maculatus (F.).
”\he experiments were carried out in the laboratory at
26±1’C, 6±1’C and 60±5% RH.
A circulatory multi-flask apparatus was designed
to prOVide a fumigation chamber suitable for the test
insects.
’”R Phosphine was generated from PHOSTOXIN-pellets (product
of DEGESCH Co. FR. of Germany).
Carbon dioxide was prOVided as a pure gas of 99% in
a pressure cylinder, which was connec ted with a pressure
regulator.
Results obtained could be summarized under the
following topics:-
1. Efficiency of phosphine against Ysrious s.tsles of the
tested insects:
Fumigation tests were conducted with fixed concentrations
of phosphine (20. 40 and 80 vpm) at Yarying exposure
periods.
”lht ~(esults ~~e4 showed that adults of h oryzae (L.),
R. dominica (F.) and C. macu1atus (F.) proved to be the
most susceptible stages to phosphine at 26±1·C and 6±1·C.
The time of exposure was a more critical factor of dosage
than the concentration of phosphine.
J fLow ”-v~ J
Phosphine was ~more effective at higher temperature
against all stages of the three insect species tested than
at lower one. For example, with a concentration of 80
vpm phosphine, the exposure times for 100% mortality in
case of h oryzae were (0.9, 9.8, 8.7 and 8.0 days) at
26±1·C and 3.3, 15.6, 12.3 and 47.0 days) at 6±1·C for
adults, larvae, pupae and eggs, respectively.
The corresponding values in case of .!h. dominica were
(0.9, 26.4, 9.4 and 11.9 days) at 26±1”C and (4.9, 88.0, 159.3
and 70 days) at 6±1·C for adults, larvae, pupae and eggs •
were (2.6, 7.3, 10.3 and 18.9 days)
at 26±1·C and (2.8, 39.5, 30.9 and 58.9 days) at 6±1·C
These values
for the various developllHlntal stages of £:.maculatus,
respectively.
By comparing the exposure time values required to
obtain 100% kill for the different stages of the tested
insects at 26±loC and 80 vpm phosphine, it vas found that ----
the adult stages of the various insects were .ore susceptibLe
to phosphine than the immature stages. The adul ts of
~ maculatus were much more tolerant to phosphine than
the adults of both ~ oryzae and ~ aominica.
Larval susceptibility to phosphine was in descending
order C. maculatus·larvae, ~ oryzae-larvae and R. dominicalarvae.
Pupae of ~ maculatus were somewhat more tolerant
to phosphine than pupae of both ~ oryzae and R. dominica.
Eggs of ~ maculatus were much more tolerant to
phosphine than eggs of ~ dominica and ~ oryzae.
2. Toxicity of carbon dioxide in controlled ataosphere (CA)
to the tested insects:
Studies carried out in the laboratory at 26±loC and
6±loC to evaluate the efficacy of various CO2 concentrations
(12.5, 25, 50. 75 and 100% v/v) in controlled atmosphere
(CA) for controlling the various stages of ~ oryzae,
~ dominica and ~ maculatus showed that carbon dioxide
was more effective at higher temperature than at lower
one and insect mortalities were increased generally as
the concentration of CO2 was increased.
Adults of ~ oryzae were the most susceptible stage
to CA contained various concentrations of CO2 followed
by larvae, eggs and pupae. when the resul ts were compared
at the LTgO level and 26±1’C. The same trend was also
observed at the lower temperature for atmospheres contained
CO2 concentrations between 12.5-75% v/v •
Results revealed also that at the two test temperatures
adults of !.:. dominica were the most susceptible stage to
CA contained CO2 at the LTgO level followed by larvae,
eggs and pupae.
By comparing the susceptibility of the different stages
of .£.:. maculatus at the LTgO level, it was found. that at
26±1’C the order of tolerance to CA contained 25, 75 and
100% CO2 was in decreased order pupae > larvae > eggs >
-
adults. At 6±1’C the order of tolerance to the various
CO2 concentrations was also pupae > larvae > eggs > adults.
The lethal time values recorded for the adults of
the tested insects at the lower temperature in CA contained
100% v/v CO2 were higher than those obtained in CA contained
75% v/v CO2 and this result could be due to nearly total
depletion of oxygen in the CA of 100% CO2•
3. Toxicity of mixtures of phosphine plus carbon dioxide to
the tested insects:
The effect of addition of 25 and 50% CO2 to 20 and
40 vpm phosphine was studied in the laboratory at 26±1’C
and 6±1’C for controlling the various stages of S. oryzae
(L.), !.:. domioica (F.) and .£.:.: maoUilatus .(F.).
obtained showed the following:
Results
• Time to mortalities were shorter at higher temperature
than at lower one. • The adult stage of the tested insects
was the most susceptible stage to the mixtures of phosphine
+ carbon dioxide at the two test temperatures.
The lethal time values required for a certain mortality
were generally reduced in the presence of carbon dioxide
at the two test temperatures. For example at 26±loC the
lethal exposure values needed to obtain 90% adult mortalities
were ( 17, 16 and 22 hr) with 20 vpm PH3 alone and
13, 4 and 14 hr} by a mixture of phosphine + 25% CO2 and
(11, 7 and 5 hr) by a mixture of phosphine + 50% CO2 for
~ oryzae, ~ dominica and C. maculatus, respectively.
The corresponding values at 6±loC were (119,98 and
122 hr) wi th phosphine alone, (50, 11 and 17 hr) by
a mixture of phosphine + 25% CO2 and (41, 11 and 12 hr)
by addition of 50% CO2 to phosphine, for the various insect
species, respectively.
For the larvae and at high temperature, times to 90%
mortali ties were (51, 44 and 67 hr) with phosphine alone,
(31, 35 and 66 hr) by phosphine + 25% CO2 and (29, 37 and
28 hr ) by a mixture of 20 vpm PH3 + 50% CO2, for the
forementioned insect species, respectively.
The corresponding values at lower temperature were
(162, 282 and 211 hr) with phosphine alone, (58, 94 and
64 hr) by a mixture of phosphine + 25% CO
2
and (49, 49
and 82 hr) by a mixture of phosphine + 50% CO
2
,
For the pupae and at 26±1 DC, the lethal time values
required for 90% kill were (51, 133 and 60 hr) by phosphine
alone, (39, 70 and 43 hr ) by phosphine + 25% CO
2
and (43,
69 and 58 hr) by a mixture of 20 vpm PH
3
+ 50% CO
2
’. for
S. oryzae, ~ dominica and ~ maculatus, respectively.
The corresponding values at 6±1 DC were (141, 267 and
158 hr) by phosphine alone, (87, 95 and 113 hr) by phosphine
+ 25% CO2 and (99, 83 and 122 hr) by a mixture of phosphine
+ 50% CO2, for the forementioned insect species,
respectively.
For the eggs and at 26±1 DC, the lethal exposures for
90% mortalities were (122, 133 and 120 hr) by 20 vpm PH
3
alone, (77, 62 and 68 hr ) by phosphine + 25% CO
2
and (61,
37 and 44 hr) by phosphine + 50% CO2•, for the vario~s insect
species, respectively.
The corresponding values at 6±1 DC were (261, 278 and
254 hr) with 20 vpm PH3 alone, (102, 119 and 119 hr) by
phosphine + 25% CO2 and (106, 42 and 103 hr) by phosphine
+ 50% CO2’ for the various insec t species, respecti vely.
The same trend was also obtained with mixtures of
40 vpm PH3 + 25 and 50% CO
2
the tested insect species at
for ~he jifferent stages of . . .
the two test temperatures.
Results revealed also that addition of CO2 to phosphine
increased the efficiency of phosphine at the LTSO level
inducing an additive or a synergistic effect on mortalities
of the various stages of the insect species tested.
At the LT99 level, the
increased also the efficiency
and larvae of h oryzae, R.
addition of CO2 to phosphine
of phosphine against adults
dominica and C. macu1atus.
But for pupae and eggs, the addition of CO2 to
phosphine induced, in some cases, an increase in the
efficacy of phosphine. and in other cases an antagonistic
effect was obtained.