الفهرس 
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Abstract
SUMMARy
The present study was carried out throughout a period
of about three years (1983 - 1985) in the experimental farm
and laboratory of the Faculty of Agriculture~ Menoufia University,
to throw the light on the tomato whitefly, Bemisia
tabaci (Gena.) and its natural enemies from different points
of view. The obtained results can be summarized as follows:
V.LA. Population dynamics of B. tabaci immature stages on
different host plants :
Numbers of eggs, larvae and pupae of ~. tabaci
were counted / 40 in~ of leaves in fortnightly samples collected
from different host plants cultivated in three plantation
and throughout two successive seasons(198J/84 and 1984/85)
a. Summer plantation :
In both seasons the highest peak of immature
stages·abundance was detected on August in cases of vegetable
marrow and cucumber, on September for pepper, soYabean
J
and cowpea. While on leaves of tomato, eggplant and okra,
the highest numbers of immature stages: were counted
o~ October.
Data indicated that the two cucurbitaceous
plants (cucumber and vegetable marrow) were the most preferred
thaD all other plants for the Whitefly infestation as
in all cases. the two hosta harboured the highest numbers
o~ the pest immature stages. Eg8PIan t, bean, tomato and
sOyabean followed,respectively, the preVious crops in the
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rate of infestation by B. tabaci imm~ture stages. While the
least rates of infestation were recorded on okra, cowpea,
and pepper plants,respectively.
b. Winter plantation :
Infestation with~ tabaci started on most host plants
when ’were still young. Population of the whitefly immature
stages increased on host plants on the first week of November
in both Eeasons. fhe lowest numbers of ~. tabaci immature
stages ,throughout the whole growth period of both seasons, were
found on broad bean and peas. In the first season, the highest
peak of abundance of the whitefly immature stages occurred on
November 5~ ; 4”5eggs and 63·larva.e/40 1n2 of tomato leave SJ
653 ”eggs and 474 larvae on cabbage; 482 eggs, 502 larvae
and 4 pupae on bean; 889 eggs, 795 larvae and 52 pupae on vegetable
marrow and 734 eggs, 647 larvae. and 38 pupae on Cucumber.
On potato the highest number of eggs (174 eggs) was counted on ”
December 2ES ,while the highest numbers of larvae and pupae
were counted on January l£!!.1(26 larvae and 34 pupae). In the
second sea~on}the peak of abundance accurred on October 20th
for cabbage, cauliflower, bean and vegetable marrow (45, 30,
58 &- 10.9 eggs ./40 in~ of leaves, respectively), on November
17la in Case or tomato (47 eggs), and ’on December ’15th ,for potato
(122 eggs). GenerallY,the populationswere lower than thoee
recorded in summer plantationsauring both seasons.
c. Early summer plantation :
Low numbers of ~. tabaci immature stages were counted on i
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the first, sa,tnples.or the’most host plants -except. cucumber
and vegetable marrow. The,numbsrs of pest immature stages fluctuated
throughout the successive samples, but with general
tendency to increase, successively, until reaching the peak
t
and this high abundance continued in some cases in’April’
of population during July’ and August (in both seasons)
and June (cucumber and vegetable marrow).
The infestation by B. tabaci on summer plantation was
more severe than on winter and -early summer plantation, respectively.
Also, the rate of infestation increased continollSly
and reached its maximum about the time of harvesting on
most host pla~ts during summer and early summer plantations.
While,in winter plantation the infestation by B. tabaci
started with relatively higher numbers. then decreased until
harvesting.
B. Host preference by B. tabaci under field conditions:
A significant F value at(5 % probability
level)w8.s detected between mean numbers of H’. tabaci immature
stages/40 in~ of leaves on different host plants in each of
the three plantations.
Plants of summer plantation could be arranged
desce...ndinglyaccording to the. the rate -.oftotal-infestation as :cucumber,
vegetable marrow, eggplant , bean, tomato, soyabean,
okra, cowpea, and pepper. Accordingly,these hosts were
divided into four groups; severly infested group.included
cucumber and vegetable marrow; heavily infested, eggplant
201
and bean; moderately infested plants, to~~to, soyabean and
okra;and slifhtly infested group which included cowpea ~nd
pepper.
In winter plantation, host plants were separated,
.significantly,into three main Groups according to the descending
order of the rate of infestation. The heavily inf-
Ested group included cucumber and vegetable marrow. ModEratly
infested plants were cabbage, cauliflower, potato, bean
and tomato. While the slightly infested group included
peas and brOad bean.
Host plants in early summer plantation were collected
together according to the infestation rate as; cucumber,
vegetable marrow and eggplant as highly i:.fested group
followed by bean, okra soyabean and potato as the moderatly
infested group, while the remaining host plants
(cotton, tomato, cowpea and pepper) r-ankad as the least
Lnf’e s ted group.
The rate of infestation with B. tabaci immature
stages on different host plants varied also, significqntly
according to the planting date. In both seasons, plants Qf
the summer plantation showed the highest rate of infestation,
followed with those of the winter plantation. Those
of the early summer plantation harboured, on the other
hand, the least numbers of immature stages on cowpea, pepper,
peas and broad bean, respectively.
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c. Preference of B. tabaci to infest plants of
different families :
The mean numbers of B. tabaci eggs, larvae
and pupae counted on 40 in~ of leaves of plan• ts belonging
to different familie s were compared for the three plantatiOns
and t hr-o ughou t the two successive seasons. In
all caae ajt t was clear that the plants of family cucu=bitaceae(
represented by cucumber & vegetable marrow)received
the highest numbers of B. tabaci immature stages •
The plant. families were arranged according
to the rate of infestation in a descending order as Cucurbitaceae,
Solanaceae, Leguminoseae and .Malvaceae for the
summer plantation. In the winter plantation,the order of
plant families infestation was Cucurbitaceee, Cruciferae~
Solanaceae and Leguminoseae. In the early summer plantation,
the Cucurbitaceae plants, also harboured the highest
numbers of the whitefly immature stages but followed by
plants of family Solanaceae, l~lvaceae and Le2uminoseae.
D. Total infestation by ~. tabaci immature stages to
different host plants under field conditions:
~. tabaci immature stages (e6&’ larvae and
pUpae were counted on different host plants throughout the
whole growing period of each host plant in three plantations
during each season. Accordingly, the inspected hoat
plants could be divided into three groups:
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1- Most preffered or heavily infested plants; c~c~mber,
eggplant, vegetable marrow, bean, cabbage, cauliflower
and soybean.
2- Intermediately infested plants : tomato, okra,potato
and cotton.
)- The least infested plants : cowpea, pepper, peas and
broad bean.
V.2~1.Relationship between the kind of host plant and B.
tabaci infestation:
Ten host plants were checked for their attractiveness
to ~. tabaci females. Twenty four hours after
releasing the adults in cages containing different host
plants, the highest number of adults was attracted to cucumber
leaYes (20.8 %~.Vegetable marrow came the next
(17.37 %), Rnd that was followed by bean (12.) %), soyabean
(11.5 %), tomato, (8.5 %), eggplant (8.5 %) cotton(7.5%)
okra (7.0 %) cowpea (3.8 %) and pepper (1 %).
Another experiment was carried out to study
the rate of eggs deposition by ~. tabaci females/24 hours
on each of the mentioned host plants. The highest rate of
eggs deposition occurred on each of tomato and cucu~ber
(105 eggs/IO females), followed by vegetable marrow (10)
eggs), eggplant (102) and bean (101 eggs). While 99, 99
96 eggs were deposited on soyabean, okra and cotton. The
least numbers of eggs were counted on cowpea and pepper
()6 and 19 eggs, respectiv€ly).
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concernt ng the mortality rates amongst immature
stages, it was generally observed that, these rates were
affected by the ir:fested plant species- High mortality rates
were recorded on tomato (83.81%),cowpea (77.77%), pepper
(68.42%), okra (61.61%) and cotton (55.2O%).~ Lower percentages
were recorded on soyabean, bean, eggplant, cucumber and vegetable
marrow (39.38%, 26.73%, 26.47%,23.82% and 19.41 %,
re spectively) •
V.2.2. Durations of B.tabaci immature stages on different
host plants:
A semi-field experiment was conducted to study
the durations of immature stages, outdoors, on the mentioned
10 host plants. Data indicated that, B. tabaci
developed from egg to adult on all the tested host
plants. The durations of egg, larval and pupal stages and
the total life-cycle did not show any sighificant differenee
by rearing on different host plants according to 1.S.D. value
when- the pest -waa .. reared on this group l:.~ cotton, soyabean,
cucumber, okra, bean and vegetable marrow. The total
life-cycle took,significantly.longer period on cowpea, pepper,
tomato and eggplant than in case of the first group.
V.2.3. Relationship between the host plant species and the
fecundity and longevity of B. tabaci females.
The mean number of eggs laid by ten B. tabaci
females on ten host plants varied considerably. The highest
rate of egg reproductivity(216 .:t 28.33,47-290) eggs/IO fem205
ales)waa recorded on cucumber, while the lowest number was
de tected on peppe rt 38.2 .:t 6.06, 17 - 70 eggs) • The whi tefly
eggs productivity on different host plants could be arranged
descendingly as : cucumber, vegetable mar-r ow, ,eggplant,
soyabean, tomato, bean, cotton, okra, cowpea, and pepper.
The oviposition period and female longevity also varied on
the different host plants. The shortest periods were associated
with adults produced from progeny reared on pepper,
cowpea, okra, and cotton. while the longest periods occurred
by rearing on tomato, eggplant vegetable marrow, cucumber,
bean, and soyabean, respectively.
V.3. Ecological studies on the natura.l enemies of B. tabaci
V.3.1. Survey of ~. tabaci natural enemies:
a. Parasi toids
Two aphelinids, Eretmocerus mundus Mercet
and Prospaltella lutea Masi (Hymenoptera), were the parasitaids
that have been found emerging from B. tabaci larvae and
pupae throughout the whole period of study.
b. Predators :
rhe following predators were found feeding on
one or more of B. tabaci immature stages in the field •
Amblyseius gossipi Elbadry (Acarina : Phytoseiidee).
Cocc.inella undecilllpunctata..L. (Coleoptera : Coccinellidae).
Chrysops .carnea Stephens(Neuroptera : Chrysopidae).
Phenobremia aphidivora Rubsqner (Diptera:Cecido~yidae).
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Diseases
During summer months and early autumn an unidentified
fungus was observed infecting the larvae and pupae of
B. tabaci, infesting different host plants, c~using their
mortality.
V.3.2. Evaluation of the role of B. tabaci parasitoids
under field conditions.
:V.3.2.l. Eretmocerus mundus Mercet
a. Summer pl~~tation :
Parasitism with E. mundus started during
August on B. tabaci larvae or pupae infesting all host plants
except vegetable marrow and cucumber where low rates of
parasitism were detected earlier in both season. The maxima
percentages of parasitism occurred during August or September
on vegetable marrow (22.88%), cucumber (20.25%), eggplant
(19.4%) tomato (12.42%) pepper (19.40%), okra (15.00%), soybean,
(18.02), bean (19.36%) and cowpea (11.69%) during first
season. The second season,the same trend was observed.
Higher percentages of parasitism, generally, occurred on
pupae than larvae.
b. Winter plantation:
Parasitism by E. mundus on the whitefly
larvae or pupae occurred on the majority of samples collected
from the winter se~son host plants except broad bean
and peas. Pupae of B. tabaci showed, also, higher parasitism
207
percentages than larvae. Generally, a possitive relationship
was noticed between the nu~ber of parasitized individuals
and those of B. tabaci larvae and pupae in the field.
’c. Early summer plantation:
Parasitoids on larv~e and pupae of B. tabaci
infesting early summer host plants (tomato, eggplant ,pepper.
potato, okra, cotton, and cowpea) appeared, generally,at late
time. The maxilIlimapercentages of paraai tism were detected
at the time of harvesting. The same trend of increase in parasitoidsl
population towards the end of each plantation was also parallel
to that occurred with the host pupae.
V.).2.2. Activity of Prospa1tel1a lutea on larvae and pupae
of B. tabaci :
a. On summer plantation
Parasitized larvae and pupae of B. tabaci
by P. lutea were noticed earlier than in case of E. mundus.
In both seasons, parasitism started with low rates~ b~~~
rates reached their maxima during September or October according
to the host plant species and at this time the parasite
was more effective on the host larvae and pupae. The parasitism
percentages by P. lutes were more pronounced on pupae
than on larvae •.
b •.On winter -plantation :
P. lutea parasitized B. tabaci larvae
and pupae infesting all winter plantation host plants except
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broad bean and peas. The parasite started its activity
earlier on some host plants than others .In both seasons,
the parasitism percentages by P. lutea were.also, lower in
winter plantion than in summer plantation.
c. On early summer plantation:
Parasitism by P. lutea on larvaeand pupae of
B. tabaci on different host plants cultivated in early summer
plantation started in June or July. However?lower percentages
of parasitism occurred on cucumber and vegetable marrow
during A~ch and reached their maxima during July.
The parasitism percentages varied according to
the sampling date, the plant species Qnd the plantation.
The host plants could be arranged desce~dingly depending
on the recorded pecentages of parasitism on these host plants
as : eggplant, soyabean, po tato, vege table marrow, cucumbar-, bean,
okra, cot ton, cauliflower”, cabb’1get tomato, cowpea and pp.pper.
The parasitoid P. lutea was more dominant than E. mundus
during summer and early summer plan tationa • W~lile,o.n the
contrary, during winter p Lan tatLon, E. mundus was more efficient
in controling B. tabaci than P. lutea during both
seasons.
V.].3. Fluctuations in parasitoid numbers and tte percentages
of pare.sitism b:lE. mundus and !._ lutes on ~ tabaci
in the field.
The numbers of !. ~~~dus adults counted
209
throughout the first year of study (1983/84) indicated the
presence of f~ur peaks of the parasite abundance; those
occurred on August, 20th. (1952 adults indicating the highest
peak), September 17th, November 5th, and
- - t
January 14~h (70 adults indicating the lowest peak of abundance).
In the second season (1984/85), four peaks of abunda.
nce were detected on July 28th, Spe tmber 8th, January
26th. and May 18.th (19, 1562, 33
tively) •
aJld 15 adults, respec-
Concerning the counted adults of P. lutea, four
peaks of abundance were detected in the first year; those
estimated 1976 Adultson August 20th.indica ting the highest
peak, 1078 individuals on September 17th 35 on January
14th. a.nd 17 adults on Uay 19th showing the lowest peak of
the parasite abundanceo In the second season, three peaks
of abundance occurred 011 June 16!hj August 9th and May 18th
(31, 1974, and 21 adults,respectively).
The role played by both parasitoidsJtogther,against
B. tabaci was more efficient, in the two year of investigation,
during August, September and October and in some cases~
the pecentages of parasitism exceeded 50 %. This ~~y indicate
the valuable role played by these perasites under
Egyptian field conditions.
210
V.).4. The sex-ratio of B. tabaci par~sitoids under field
cor..c5.itions:
The monthly obta.ined ad uLts of the two paras i t-
~ oids, E. illundusand P. lutea were sexed to estimate the sexratio
in the field. The sex-ratio of E. mQ~dus (female:
male) ranged between (0.9 : 1) in February to (3.8 : 1) in August
in the .f i.ra t season find it ranged be tween (0.6 : 1) in
January and (2.8 : 1) in August during the second season.
In case of P. 1utea the sex-ratio varied from(O. 7 : 1)
in October to (2.6 : 1) in June in the first season and from
1.2 : 1 in August to 2. J : 1 in May during the second SEason.
V.).5. Efficiency of the natural enemies of B. tabaci eggs:
Throughout the two successive years of stUdy,
no parasite was detected on ~ tabaci eggs. Symptoms of
eggs predation due to predators having piercinG-sucking
mo~th-parts were, on the other hand, noticed on many eggs
The percentages of predation amongst the collected B. tabaci
eggs ran&ed from 0.74 in March to 13.89 % in November in
first season and from 0.0 in January and February to 22.01%
in September in the second season •
V.3.6. Efficiency of the natural enemies of B. tabaci larvae
and pupae under field conditions.
The role of parasitoids, predators and fungus
in suppressing the populations of B. tabaci larvae and pupae
was estimated. Regarding the monthly records of the total
211
percentages of ~. tabaci individuals attacked by natural
enemies, they ranged from 7.66-40.63% for larvae and from
lO.11-89~5% for pupae in the first season. In the sEcand
season (1984/85), these pereent~es estimated 6.85-72.19%
,
for larvae and from 0.0 to 87.40~ for pupae. The period
that extended from June to January could be considered as
a period of higher efficiency of natural enemies against.
the host larvae and pupae.
V.3.7. Activity of B. tabaci parasitoids on another aleyrod:
i.dspecies :
The aphelinid parasi tes, Prospaltell~ lutea Masi
and EretmocerU9 sp. were found parasitizing pUpae of
Aleurotrachelus citri Priesner & Hosny during the whole
period of stUdy. The percentages of parasitism by P. lutea
ranged from 0.0 to 40.68% in the first season, while it
ranged between from 0.0 to 20.46% in the second season.
Generally, the recorded percentqges of parasitism by E. lutea
were lower in this case, than those recorded on B. tabaci •
V.4. Biological ~nd ecological studies on Prospaltelle lutea
Masi (Hymenoptera: Aphelinidae):
V.4.1.A. Biology of Prospaltella lutes Masi :
The egg, the three larval instars, the prepupa
the pupa and the adults (males & female) of E. lutea were
described. At 30 1: O.14°C. and 60 - 75% R.H., the durations
o~ the egg stage and the three larval ins tars averaged
2.2 1:. 0 •8, 2.7 1:. 0 .11, 3.6 .:! 0 •11 and J.l .:t 0 .14 days,
respecti ve ly. The pupal d~ation lasted 5.9 ~ 0.46 and
212
6.8 ~ 0.19 days for male and female,respectively. Subsequently,
the total developmental period of male and female
P. lutea averaged 17.1 Z0.67 and 18.4 ± 0.29 days, respectively.
The processes of matir.g and ovipostion were described.
Under laboratory conditions, the adultP. lutea female
laid an average total numbe r of41.S,;t2.96 eggs throughout an
oviposition period of 9.15 ~O.77 days.
In few cases,3utoparasitiem occurred, but this
phenomenon was, generally, rare and it may be attributed
either to the low density of the unparasitised hosts or to
the instinct error of female parasite.
B. Preferenece of B. tabaci stages and instars for parasitism
by P. lutea females and effect on the resultant
adults.
The percentage of parasitism, parasite lifecycle,
parasite emergence and longevity of the resultant
adults were studied when the different larval instqrs or
the pupae of !:. tabaci were exposed to P,. lutes. mated females
for parasitism. Data indicated that the 3rd instar larvae
of the host, followed by the pupae were the suitable stages
for rearing the parasite. While, parasitism failed, completely,
on the first instar larvae of B. tabaci •
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.”V.4.2. Effect of the kind of food and temperature on P.
lutea adult longevity :
Vilienfed on four different food materials
(bee honey, maize pollen grains, mixture of~honey and maize
pollen grains 1:1 and water)in addition to a group of adults
kept without nutrition. The adults of P. lutea were
kept at five different temperatures (15, 20, 25, 30 and
35°C.). Relative humidity wes kept between 60 and 75 %
R.R. Data indicated that, at all temperatures, the adult
longevity was significantly affected by the kind of the
offered food and the longest life-span was obtained by
feeding on bee honey droplets.
Keping the parasite adults at 15°C. and providing
them with bee honey droplets appeared as the best conditions
for the parasite as in this case the longest adult’s
life-span was obtained and the adult’s viability was not
affected as mating and oviposition normally took place
after the preservation period.
V.4.3. Competition between t. lutea and ~ mundus to parasitize
different s~ages and instars of B. tabaci
under aboratory conditions.
Data indicate that both parasites refused
to oviposit in boidies of 1-st inster larvae of -B. tabaci.
On the 2nd inster larVae are more subjected to parasitized
by E. mundus than P. lutes. On the 3££. ioster
larvae and recentaly formed pupae of B. tabaci occurred
by both parasites (P. lutes ~nd E. mundus) under loborRtory
conditions. Longevitie8 of ~dult parasitoids thRt reRuJted
on different stage were also affected by dif, ferent Rt~ges
and instars of B. tabaci. The longest period occurred
within adults emerged from 3rd instar larvae. Also, the
highest percentages of parasitism by E. mundus and P.lutea
were on )rd instRr larvee of B. tabaci (28 and 26 % ,
respectively).