الفهرس 
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Abstract
A field study was carried out in the Experimental Farm of the
Faculty of Agriculture at Moshtohor (Qalubiyah Governorate) throughout
1996 and 1997 cotton seasons to estimate the weekly relative population
density of the common predaceous insects on cotton plants sown in three
planting dates (cotton plants of two planting dates were kept free from
insecticidal treatment, while those of the third date received three
applications by the conventional recommended insecticides), and to
evaluate the changes in abundance in population of each of the concerned
predators throughout each of the two seasons. Studies included also the
rates of pink bollworm infestations to cotton pen squares, flowers and
bolls in order to find out the correlation between predator’s population
and that of Pectinophora gossypiella. Also, laboratory deposited P.
gossypiella eggs were distributed in the cotton field to estimate natural
role of predators in feeding on these eggs. On the other hand, a laboratory
study was carried out at 26±2°C and 60-70 % R.H. on Chrysoperla
camea which was found as the most abundant predator in cotton fields to
evaluate the effect of larval feeding on the pink bollworm eggs, larvae or
their mixtures at three different ratios on the predator’s immature stage
durations, adult’s fecundity and longevity, and also on the feeding
capacity. ’The obtained results may be summarized as follows:
1- Relative Population of the Most Common Insect Predators in
CottORFields :
1.1-AbuadaKe of total predators :
Data clearly, showed that the populations of insect predators were,
generally, higher in 1996 (total counts of 1648,2021 and 1007 individuals
throughout the whole season of three sowinsz dates. respectively) than
1997 cotton season (886, 691 and 358 individuals, respectively). This
may be due to the environmental conditions which vary from one year to
another, or to any other factors. The lowest total counts (l007 and 358 in
1996 and 1997, respectively were counted on plots that received
conventional insecticidal applications, indicating the harmful effect of
pesticidal application on these beneficial insects.
Regarding the weekly counts of total numbers of insect predators
on cotton plants that were kept free from any insecticidal treatment
throughout the whole period of plant growth, the population of predators
started with few individuals up to the third week of May when their
numbers increased forwardly during the successive weeks until the peak
of abundance which occurred always during June (4000 individualsl1 00
double net strokes on mid-June at 27.1°C and 66.] 3 % R.H. & 521
individuals on June 8th at 27 .17°C and 61.35 % R.H. for the two planting
dates of 1996, respectively; and 150 individuals on June 14th at 27.01 °C
and 60.56 % R.H. & 88 individualsll00 double net strokes on June 14th
also for the two planting dates of 1997, respectively). On cotton that
received insecticidal applications, the population fluctuation of total
predators took, nearly, the same trend as that on untreated cotton but with
lower abtmdance (maxima counts of 228 individuals on mid-June, 1996
and 48 individualsllOO double strokes on June 14th 1997.
Five predators were concerned in this study. Those included a
neuropteran, Chrysoperla CIII7U!Il (Cbrysopidae); three coleopterous,
Coccbtellil. alllled””.,nctIltII, SCYIIUUISspp. (Coccinellidae), and PaederllS
alfrerii (Staphylinidae), and a hemipteran, Orius spp. (Anthocoridae).
These species were found the most common on cotton plants throughout
feeding on cotton pests. The relative population abundance of each of
these predators, throughout the cotton season was estimated by weekly
counts of the nwnber of predators captured by 100 double strokes of the
sweeping net.
As for the weekly counts on cotton plants, that received the
conventional insecticidal spraying, data indicated that these five predators
took nearly the same trend of abundance throughout the season, except
for the lower counts due to the harmful effect of insecticidal spraying.
1.2- Abundance of different predators:
1.2.1- Chrysoperla cornea Steph. :
The total numbers of C. carnea adults counted throughout the
whole cotton season were 1268 & 1592 adults on cotton of 1996 season
and 305 & 271 adults on cotton plants of 1997 on the two plantations that
did not receive any insecticidal application, respectively. On cotton plants
that received the conventional insecticidal treatments, the total counts of
C carnea adults were 788 and 125 individuals throughout the whole
season of 1996 and 1997, respectively, being 44.9 and 56.6 % less than
those counted on the untreated plots. Regarding the weekly counts
of relative populations of C Cl1I7II!Jl in cotton field, data indicated one
high peak. of the adults’ population abundance that was estimated by 342
and 431 adults/I ()()double net strokes on mid-June of the 1996 two planting
dates, respectively, and by 71 adults on June, 14th and 48 adults/l00 double
strokes on June, 28th for the 1997 two untreated plantations.
1.2.2- Coccinella IlndecimJHlnctllta L. :
Total population counts of C IllfdeCimpllftdatJl, indicated that this
predator was the fourth in the order of abundance after C. carnea,
Paederus alflerii and Orius albidipennis. These total numbers were 63
& 54 adults on cotton of 1996 two planting dates, respectively, and 82 &
74 adults, on cotton plants of 1997 two planting dates. Thus indicating
that the predator was generally more abundant in 1997 than in I996
cotton plantation. Although C. undecimpunctata adults were, nearly,
detected in all of the weekly collected samples, the weekly counts of
adults were, relatively, few. Also fewer total counts of this ladybird beetle
were recorded on cotton that received insecticidal treatments (35 and 38
adults in 1996 and 1997, respectively).
1.2.3- Scymnus spp.«
The total counts of adults, throughout the whole season on cotton
plants that kept free from any insecticidal treatment were only 14 & 21
adults of cotton of 1996 two planting dates, and 101 & 59 on those of
1997, respectively. These counts represented 0.85 & 1.04 and 11.4 &
8.54 % of the total predators’ counts, respectively. It is clear that, as
occurred with C undecimpunctata, the total counts of Scymnus spp.
adults were higher in both plantations of 1997 than on those of 1996.
Only 11 and 37 adults were recorded as total counts on treated cotton of
1996 and 1997 seasons, respectively.
L2.4- Paedmls aljierii (Koch) :
The total counts of adults, throughout the whole cotton season were
146 & 189 adults for 1996 first & second planting dates, and 219 & 179
in 1997 two planting dates, respectively. Thus indicating that the predator
was more alHmdant on cotton plants of the second year (1997) than the
first one (1996). Spraying. on cotton plants by the conventionally
The total counts of the predator adults were 81 and 89 throughout 1996
and 1997 cotton seasons, respectively indicating, reductions by 51.64 and
55.28 % from those counted on the two seasons, untreated cotton plants,
respectively.
1.2.5- Orius spp. :
The whole season total counts of Orius spp. on the untreated
cotton plants were 157 & 165 individuals on 1996 first and second
sowing dates, and 179 & 108 individuals on cotton plants of 1997 two
planting dates, respectively. These data indicating that Orius spp.
occupied 9.53, 8.16,20.2 and 15.63 % of the total counts of all predators,
respectively. The total counts of Orius spp. on treated cotton were 92 and
69 individuals, respectively showing reductions in total population by
42.86 and 51.92 % than that on untreated cotton plants.
11- Pink Bollworm Infestation to Cotton Structures in Relation to
Abundance of Predators:
11.1- Infestation to fruiting structures of cotton plants:
This experiments aimed to estimate the effect of PBW P.
gossypiellll on pen squares, blooms and green bolls during the two
successive seasons 1996 and 1997.
D.1.1- Effect on pen squares :
The overall total number of infested pen squares on cotton plants
during the whole season at the three planting dates, were 25, 31 & 21 and
30, 20 & 19 infested pen squares in 1996 and 1997 seasons, respectively.
Data also, showed that the lowest overall total mnnber of infested pen
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squares was recorded on treated cotton plants, which was represented by
21 and 19 infested pen squares during 1996 and 1997, respectively.
11.1.2- Effect on cotton blooms:
Results indicated that, the blooms infestation began to appear at the
end of June or at the first half of July on the three plantations of cotton.
Also, the first peak of infested blooms was recorded during the same
period. The second peak appeared at the end of July or at the first week
of August in the three cotton plantations. While, in 1997 cotton season,
the first peak of infested flowers infested by PBW occurred in July in the
three cotton plantations. In general, the lowest number of infested blooms
was recorded on cotton plants treated with insecticides against cotton
pests.
11.1.3- Effect on green cotton bolls:
The number of infested cotton bolls was, generally, higher in 1997
than 1996 in plots of untreated and treated cotton plantations. It could be
also noticed that cotton plants of the second (treated) plantation
harboured, generally, lower numbers of infested bolls and PBW larvae
than the untreated plantations during both seasons. On the other hand, the
third (untreated) plantation (late-sown date), harboured, higher numbers
of infested bolls than the first (untreated) plantation. It could be also,
observed that infested bolls harboured higher number of small age of
PBW larvae than the other larval ages in both seasons and in the three
cotton plantations treated or untreated.
11.2- Correlation between common insects predators’ populations
and Pectinophora gossypielLa infestation in cotton fruiting
structures:
11.2.1- Correlation between common insect predators’ population and
cotton pen squares’ infestation by P. gossypielLa :
The calculated simple correlation coefficient values were
insignificant, being -0.734, -0.786 and -0.047 in 1996 and 0.101, -0.111
and 0.245 in 1997 for the three sowing dates, respectively. The
correspondent r2 values were, consequently, 0.54, 0.62 and 0.83 in the
former season and 0.01, 0.01 and 0.06 in the latter one, respectively.
1l.2.2- Relationship between common predators’ population and
infestation rates in cotton flowers and bolls :
a- Flowers:
The relationship between infestation rates in cotton flowers and
insect predators’ population was stronger in 1996 than 1997 in the three
sowing dates. Also, in the two seasons of study, highest R2 values were
detected in the first sowing date (0.71 and 0.74, respectively), followed
by the third sowing date (0.69 and 0.47), while the lowest values were
calculated from data of the second sowing date of both seasons, i.e.,
treated cotton plots (0.65 and 0.01, respectively).
b- Cotton bolls :
The simple correlation coefficient values were calculated as -0.415,
-0.386 and -0.635 in 1996 and -0.602, -0.053 and -0.447 in 1997 in the
three sowing dates, respectively, and those of R2 were 0.17, 0.15 and
0.25 in the former season, and 0.36,0.003 and 0.37, respectively, in the
latter one.
111-Efficiency of the Predators Associated with Cotton Plants
on Eggs of PBW Pectinophoru gossypiella (Saunders) :
111.1- Consumption of PBW eggs by predators :
In 1996, predators associated with cotton plants predated large
numbers of PBW eggs throughout June, the 1st half of July, the 2nd half of
August and September, in the three cotton plantations, with untreated or
treated by conventional program to control cotton pests. While, the low
number of predated eggs was recorded in the remaining inspections.
In 1997 cotton season, results cleared that the predated eggs ranged
between 0.9-1.6, 0.4-0.8 and 0.4-1.4 predated eggs/card, recorded on May
at the 1st, 2nd and 3rd planting dates, respectively. Then, eggs predation
increased in June (0.8-3.4 predated eggs/one card). While, in July and
August, the predated numbers of eggs of PBW were lower than those in
May, June and September, in the three planting dates. Also, the predated
eggs on September, ranged between 1.4-3.3 predated eggs/one card. While,
during July, those ranged between 0.9-2.6 eggs predated/one card in the
three sowing dates.
m-2- Relationship between the number of common insect predators
in cotton fields and number of predated PBW eggs fixed on
cotton plants in tbe three cotton plantations during the two
seasons 1996 and 1997 :
The predaceous insects in cotton fields fed on higher numbers of
PBW eggs throughout the following months : June, August and
September in the three cotton plantations. Also, the abundance of
predators and, consequently, nwnber of predated PBW eggs in treated
cotton (by conventional program against cotton pests was lower than in
untreated cotton plantations.
IV- Bionomics and food consumption of Chrysoperla carnea :
Study was carried out to determine and evaluate the activity of C.
carnea larval feeding on P. gossypiella eggs, 1st instar larvae or their
mixtures at different ratios, and also to study the durations of immature
stages and adults’ fecundity and longevity in relation to the mentioned
food kinds.
IV.l- Durations of immature stages:
A- Egg stage:
The incubation period of C. carnea eggs ranged from 3.44±O.1
days when larvae of this predator were reared on a mixture of P.
gossypielLa eggs and larvae at ratio 1 : 1 to 3.52±O.1 days for those reared
on mixture of one egg: 3 larvae. Thus indicated insignificant effect of the
larval diet on this period.
B- Larval stage :
The total larval period which lasted 9.14±O.26 (8-11), 10.28±O.42
(9-12)~ 12.0±0.53 (10-14) and 13.14±O.74 (10-16) days for C carnea
larvae fed on eggs or mixtures of eggs and larvae at ratios 3 : 1, 1 : 1 and
1 : 3, respectively, indicating prolongation of this period by the increase
of P. gossypiella larvae in the offered diet.
c- Pupal period :
The pupal period lasted 7.5±O.65 (6-9), 8.0±0.2 (7-9)~ 8.00±0.41
and 9.00±0.41 (8-10) days when the predator’s larvae were fed on the
prey eggs and previously mentioned mixtures, respectively.
3- Feeding on P. gossypiella neonate larvae only:
The consumption of P. gossypiella larvae by each of the three
larval instars of C. carnea are 42.52 (0-184) larvae during the lsr, 245.64
(9-519) larvae during the second and 155.2 (27-212) larvae during the
third instar larva. It is clear that the larva in its third instar fed on fewer
numbers of P. gossypiella larvae than did that of the second instar. This
may be due to that the few number (only five) that could reach the third
instar became weak due to unsuitability of P. gossypiella larvae as sole
food and consequently the predator larvae became unable to reach the
pupal stage.
IVA- Fecundity and adults’ longevity :
C. camea larval feeding of P. gossypiella eggs only led to adults
that manifested shortest pre- and post-oviposition periods; longest
oviposition period and male and female life-span (6.0±O.27, 4.33±O.88,
24.0±3.78, 24.33±5.2 and 34.33±5.69 days, respectively), and highest
eggs productivity (224±81.53 eggs/female). While, those fed on
eggsllarvae mixtures at ratio 1 : 3 led to adult showed opposite results,
i.e. longest pre- and post-oviposition periods, shortest oviposition period
& adults’ life-span and lowest eggs productivity.