الفهرس 
Acknowled gementOnly 14 pages are availabe for public view
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Abstract
_ The true egg parasite, Trichogramma evanescens (Westwood)
was recOrded as the only species parasitising eggs of Ostrinia
nublla116 (Hub.) in Egypt. Thus, this work was carried out
under field and laboratory conditions to study this tmportant
parasite, on the mentioned pest, from different points of view.
The obtained resul ts can be summarized as follows:
1. Natural role of!. evanescens on Q. nubilalls eggs:
The percentages of parasitism were estimated in 1981 and
1982 corn seasons at Kafr E1-Sheikh and Qalubia governorates.
The recorded percentages of parasitism ranged from 36.79 to
59.66% (mean 53.7%) in 1981 and 38.7-60.98% (~ean 55.9%) in
1982 at Kafr El-Sheikh governorate. Higher pe rcenta gea of
parasitism were, generally, detected at Qalubia governorate
(56.86-59.9; mean 58.17% in 1981, and 55.74 - 61.321 mean 58.08~
in i982). The obtained reBUlta, in both localities, indicated
increased ac’tivity of the parasite as the season advanced. T~e
recorded data, also con:fl.xmedthe 1mportan t role played by the
parasite in suppressing the egg population of the ECB in Egypt,
where the percentage. of’ parasitism, in most cases, were higher
than 50%.
The parasite mortality percentages inslde the parasltlsed
hoa t eggs, at Kaf”r Bl-She1kh governorate, were the highest
amongst eggs of· the f’1rBt a_pIe that collected at the beginning
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of September (11.32% in 1981 and 17.24% in 19
82
). The
percentages mort81ity were greatlY lower amongst the remaining
samples; ranging from 2.56 to 5.85%. At Qelubia
go~ernorete, the recorded percentages of mortality reng
ed
from 3.64 to 1.46%.
2. Effect of field application of corn pests insecticides --
on -T. -evanescena:
The effect of field application of each of five insecticides;
Garbaryl (Sevin, w.p.85%.Malathion E.G. 57%) ,
Dicofol (KeHhane E.G.18.5%) ,Endosulfan grenules 4% end
Methomyl (Lannate s.p.9O%) at the recommended rates, on’
the percentage of parat:1em on £.nubllaliS eggs and p8llaite
mortality in the host eggs, weB estimated. Results indicated
that 24 hours after insecticidal application, ell of the
tested insecticides, except Endosulfan, reduced s~verely
the percentage of parasit1sed eggs (9.4,17.6,15.3,49.6 end
15.5% for the pre~ious insecticides, respecti~ely,compared
with 57.1% parasitism in control plots). Se~en days after
treatment, the severe effect of Methomyl waS completely removed
(52.4% parasitism, compared with 59.2% in control)
indicating short residual effect of thiS insecticide. But
the drastic effect of oerbarY1, lIalathl.Onend Dicofol
.as st111 detecte4 • After 14 QayS of applicatiOn,
the recorded. perc ••.t•a.ges of parasitimn in treated
plotS increased , but the highl.y significant
.-~---~~ ----------------------------------
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reduction in % of parasitiem occurred in treatments witb
carbaryl,llalathion and-Dicofol indicating long residual
effect of tbese insecticides- Tbe same trend of insectioidal
effectiveness ~s also detected on the parasite mortality
percentage after 1, 7 and 14 days of applioation.
Accordingly, Endoaulfan \f&8 reoommendedfor corn borers
control as it, slightly, affected the parasite activity.
ii.-tbaalY
111l
S3be used but , at leas 10, 7 days before paras it e
release. Field applications with Oarbaryl,Malathlon’,DlcDf
o
l
or llethoiaYlIIDlStbe preceded by est:\JllStions of the natural
percentage of parasitiem by 1_ evenescens, so that insecticidal
applications can be done in periods of low parasite J
population to avoid the drastic effect of these insec·ticides
on the beneficial role of the parasite.
3. Effect of parasite-host ratio on the occurrence of .
~peEPsrssit1Sm and effects on the resultant ~ro,en;y’
Under field conditions’, data indicated that superparasitiem
by 1. e.•anesoens in ~- DUbllalis eggs rerely
occurred, as the average, nUJllber of adults emerged/paraslt1sed
host egg, in 1981 and 1982 seasons, at Kaf’r Bl-She1kh
and Qalub1a governorate. ranged ~froa 1.01-1.06.
In the laboratOrJ t five replicate. (of 60 ho.t eggs
.~
each) were expos. ed to 1, 3, 5, 10 and 15 pairs of 1f~.’Y8XleBeelll1 - .-..-,,;;;;;;;;;;.;.,;;:;--~
_94 -
for 24 hours. Results indicated that the probability of
occurrence of superparasitism increased with the increase
in number of !. evanescens couples/GO hoat eggs.
The highest percentage of superparasitism occurrence
(25.76% of parasitised eggs) occurred when 60 host eggs
were exposed to 15 pairs of the parasite. This highest
percentage of superparasitism occurrence was associated
with the highest % of parasite mortality inside the par
a
-
sitised host eggs (9.8%).
Fecundity and longevity of the resulting progeny,al
so
,
decreased as the percentage of superparasitism increased.
The obtained results, generally, 1nd~cated that superpar
a
- -
sitism by T. evanescens in O. nUbi~alls eggs is an undea1r- - - able phenomenonas it increased parasite mortalities’in host
eggs, and reduced activity and fecundity of the resultant
offspring. Data, also, indicated that the opt~um parssitehost
ratio for laboratory rearing and field release of the
parasite was 5 pairs of the parasite / 60 host eggs(3 egg
masses), as in this case slight occurrence of superparasitism
(0.79%), lower percentag~ of parasite mortality 10 host eg~
(5.9%), higll percentage of parasitism (90.3%) ””d,relatively,
high productivity of the rellUltlng offspring (711 adults /
10 females) were detected-
4- Suitability of s_nubilaliS egg age for parasitism:
Freshly laid eggs of -o. uubUalis and those of 24,48
- -- -~---- ---
~-~--- - -- -- -- ,.
- .95 -
and 60 hours old were exposed to!. evanescens adults for
3 hours. On freshly laid eggs and those of 24 hrs. old •
higher numbers of the host eggs were parasitised (646 and
656/50 paraaitefemales, respectively). On eggs of 48 and
60 hours old, lower numbers of eggs were parasitised (430
and 199, respectively). Also, in eggs of 48-60 hrs. old,
high mortality percent ages (14.5 and 27.5%.res pect ive ly 1
inside the host ~ggs were recorded. However, these percentages
were greatly lower in freshly laid and 24 hrs.ol
d
eggs.
ThuB, indicating that .2.. nubUal1a eggs are more suitable
for parasitism during the first 24 hours after deposition.
Studying the effect of Q. nubilalis egg age on the off-.
spring, also, indiceted higher productivity and longevity
of:”adults resulted from host eggs parasltised during the
first 24 hours after deposition. Older eggs gave adults of
low productivity and short life-span, and thus, considered
unsuitable for successful parasitism.
5. Effect of different re tmes of nutrition on araslte
longevity and produotlvltls
The obtained results indicated that adults fed on 20~
sular solutiOn showedthe hl8best productivi 1;)’ (576 puedte
sAulte/50 pairs ef the p&rBll1U). Adults fed on 100 ”
bee hone)’ ranked the eecond (514 adUlts/50 pares1te-coUplell).
These nutritive solutions caused the lo_eat percentages of
parallite mortality in host egga(6.1 and 7.1l’,respeeti’lel)’).
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On tne resultant offspring, tne sBIDe solutions (20% sugar.
solution and 100% bee noney) were aesociated witn nignest
total productivity of tne offspring (97.
6
and 95.8 adul
ts
/
female, respectivelY) and longest meles end females longevity.
AccordinglY, tnese two nutritive solutions were recommended
for parasite laboratory rearing and before parasite release
in the field.