الفهرس 
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Abstract
- The present investigation was carried out to
estimate the ~ortalities amongst the pink bollworm,
Pectinophora gossypiella (Saund.) larvae at different
districts of four Egyptian governorates, and the role
played by bacteria, virus, other mortality factors
and natural mortality in causing mortalities amongst
dead larvae, and to study the effect of the bacterium,
Bacillu~ thuringiensis Ber. (in commercial preparations)
on larvae of !. insulana and P. gossypie1la; the effect
of field application of Eactospeine (a commercial
preparation of ~. thuringiensis) on the larval popula-
<~tion of P. gossypiella and the fecundity of resultant
adults. The obtained data can be summarized as follows:
A. Natural infection of E. gossypiella larvae with
diseases and other mortality factors :
Larvae of P. gossypiella that were counted in
fortnightly samples, of 100 cotton bolls each, collected
during September and October, 1980 and 1981, at
different districts of four Egy;tian governorates
(FaJ<Toum,QalUbia, ShaI’k:,’”ia and Gharbyia). Collected
larvae were reared in the laboratory until pupation
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and adults en:.ergence. where li””ortatlies anonga t
larvae and subsequent pupae and the percentages of
adul ts eLlergence were recorded. Dead larvae were
thoroughly ins)ecteci to detenJine the cause
of death. The highest percentages of total mortality
was recorded at Sharkyia governorate (30.62 %. average
of two seasons) and that was correlated with the lowest
larval population that was co~~ted at the same governorate
(68 larvae/IOO cotton bolls; average of two
seasons). The lowest total mortality percentage (27.14%)
was oD,the other hand, recorded at Fayoum governorate,
and that was correlated with the highest rate of infestation
that was recorded at this governorate (100.2
larvae/IOO bolls). That gave an indication that the
natural mortality factors may playa role in suppressing
the rate of infestation with ~. sossypiella in cotton
fields.
Studies on the percentages kill by different
causes, amongst dead larvae, indicated that the majority
of dead larvae were killed by bacteria (53.57 - 80.28 %
of dead larvae). Virus ranked the second after bacteria
at Fayoum governorate (19.41 % of dead larvae).
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Estimation of the rate of natural infection of
P. gossypiella larvae, in the field, with diseases
and other mortality factors before planning for any
program of the pest management is recommended.
B. Laboratory infectivity tests with B. thuringiensis :
8.. On the first instar larvae of E. insulans. and
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~. gossypiella :
Pour concentrations in water of each of the two
commercial preparations (Dipe1 and Bactospeine) were
used in this experiment; 0.05 % (8 x 103 l.U./ml. suspension),
0.1 % (16 x 103 r.U./m1.), 0.2 % (32 x 103
r.U./ml.) and 0.4 % (64 x 103 I.U./ml.), using the
dipping technique of okra disks or green cotton bolls. The
obtained data indicated that Dipel w8S,generally,more efficient
on !. insulana 1st instar larvae than. Bactospeine,
where the averages of values in percentage mortality
after 7 days of treatment, % of malfor.med pupae, LeSO
end ~50 were 55.4 %, 12.2 %, 0.0675 % (lO.B x 10
3 I.u.I
mI.) and 5.9 days in case of Dipel treatment and S3.6 %,
9.03 %, 0.1 % (16.5 x 103 l.U./m!.) and 7.0) days in
case of Bactospeine treatment, respectively. On~.
gossypiel1a l~ instar larvae, Bactospeine treat~ent
showed that -E. insulana 1-st instar larvae were more
auaceptib2e, where ~he L050 in case of the former insect
was 0.15 % (24 x 103 r.U./ml. suspension).
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b. On the 2~ and 4t&-instar larvae of P.gossypie11a: -------~-----------------------------------------
Five concentrations of Bactospeine were 1ncorporated
with the larval artificial medium (80, 160, 240,
320 and 400 I.U./7 gm. diet) and tested against 2ll£ and
4th instar larvae of ~. gossypiella. The illustrated
concentration-mortality lines indicated that the effect
increased with the increase in the bioinsecticide concentration
and the decrease in larval age. The LeSO
values were 154.7 and 429.8 I.U./7 gm. diet for treatment
of the 2~ and 4!a insters, respectively. The LTSO
values averaged 3.15 and 11.15 days, respectively,
indicating higher susceptibility of the former instar.
A latent effect could be, also, detected amongst the
resulting pupae and adults emergence, but the effect
was generally low.
c. On resting larvae of l.. gOBsypiella. :
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Intrahemocoele injection of five doses of Bactospeine
(8, 16, 24, 32,and 40 I.U./larva)was carried out
in healthy diapaused larvae of l.. gossypiella. Yortalities
amongst treated larvae increased, successively
during the first 3 days after treatment, though the
highest mortality rates occurred after 24 - 48 hours
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of’ treatment. kiter the Jrd day of treatment; mortalities
amongst treated larvae were very low. As the
applied dose increased; the effect on larval
mortality increased, however the LTSO value decreased.
The ~50 after 72 hours of treatment was 11.29 r.u./
larva.
c. Effect of field application of Bactospeine on !.
gossypiella :
Bactospeine suspensions were applied on cotton
plants (sown at two
28th) at two rates;
of water/fedden and
planting dates; Karch, 7i!! and
2.5 Kg. (40 x 109 1.U.)/200 litres
9 .
4 Kg. (64 x 10 I.U.)/feddan.
Bioinsecticidal application took place on August, lOth
on the two plantations. Data indicated that treatments
caused a significant reduction in larval population
of P. gossypiella than control. The percentages
of reduction in larval population averaged 47.11 and
35.16 %, respectively for the first plantation and
31.15 and 33.84 %, respectively for the second plantation.
Thus the low rate of Bactospeine (40 x 109
I.U./feddan) was recommended.
The oviposition rates amongst adults that developed
from larvae of treated and untreated areas were,
also, estimated. Data indicated that treatments,
markedly, reduced the females oviposition rate. However,
a slight effect on the percentages of eggs hatching
was detected.