الفهرس 
IntroductionOnly 14 pages are availabe for public view
 |  | from | 202 |  |  |
| | | from | 202 | | |
Abstract
The present study was carried out in two plantations of maize
(Summer and Nili) cultivated in Moshtohor Fac. of Agric.Res. farm during
the two successive years 1995 and 1996. Summer and Nili plantations of
1995 season were sown on June, 3rd and July, 7th and those of 1996 season
were sown on June 15 th and July 12 th. The study was aimed to the
following aspects:
1- Estimation the rates of damage for the major insect pests attacking
maize plants.
2- Estimation of seasonal fluctuations of predaceous insects in maize
field in different plantations.
3- Surveying and estimating the rate of parasitism by parasitoids
attacking the insect pests under study.
4- Studies on parasitoids on hibernating com borer larvae infesting
com stalks.
5- Physiological studies on the haemolymph of both active and
hibernating healthy of S. cretica and O. nubilaJis and those parasitized by
Bracon brevicomis:
The obtained results can be summarized as
follows:
I. Rate of damage for some major insect pests
attacking maize.
I.I.Rate of infestation caused by Sesamia cretica ·
Two peaks of damaged plants could be detected in both, 1995 &
1996 Summer and Nili plantations. As for, in the % of infestation for the
first and second peaks of damaged plants it were 3.2 & 3.8 % and 7.77 &
4.5 % for Summer plantations of the two years. As for the first Nili
plantation it was 4.1 & 1.8 % , wbile in the subsequent Nili plantation it was
9.6 & 2.4 %. The infestation to maize plants by S.cretica was generally
higher in 1996 than 1995 throughout both Summer and Nili plantations .
Maize plants of the Nili maize plantation harboured, generally , higher
infestation rate by S.eretica than the Summer plantation of maize was more
infested than the Nili plantation.
1.2. Rate of infestation caused by Ostrinia nubilalis
It could he deduced that in Summer plantation, infestation to maize
plants by O.nubilalis started in August on few numbers of plants.
Throughout the subsequent weeks, the rate of infestation increased
successively until reached the bighest accumulative percentage of infestation
at the end of the season (69.54 % on September, 16 th 1995 and 96.5 % on
September, 28 th 1996 .
1.3. Rate of damage caused by Spodoptera littoralis and
Spodoptera exigua
In the first Summer plantation, the highest increase in the rate of
damage ( 3.8 ) occurred in two periods, the first on July, 22 nd while the
second was detected on August, 12 th . In 1996, Summer plantation the
highest increase in the rate of damage ( 1.6 ) occurred on August, 31 st .
In Nili plantations of both years the highest rates of damage were 5.4
on Sept., 23 th; and 0.8 % on Sept., 15 th .
1.4. Rate of infestation by aphids:
In Summer plantation 1995, aphids activity started from July, 29 th
with rate of infestation 0.9 % to August, 26 th with rate of infestation 10 %.
During this period the highest rate of infestation 100 % and the abundance (
1883 aphids I plant) occurred on August, 19 th . In Summer plantation
1996, aphid activity started on July, 27 th with 5 % rate of infestation and
ended on August, 31 th with 3.18 rate of infestation. The highest rate 100 %
occurred on August, 17 th while the highest abundance 1195 aphids I plant
was on August, 10 th .
In Nili plantation 1995, aphids activity elapsed the period between
August, 26 th to Sep., 16 thowith range rate of infestation 1.36 to 40.91 %
with highest abundance 882 aphids I plant occurred on Sept., 2 nd .. While
in Nili plantation 1996, there were three slight separated periods of activity ,
the first elapsed two weeks from August, 11 th to 18 th with 35 & 21
individual aphid I plant. The second were 95.9 to 100 % infestation with 12
& 15 individual aphid / plant on Sept. 1 st to 8 th . The third was on Oct.,
13 th to 20 th with 6 to 8 individuals aphid / plant and %.infestation 1.4 to
2.4, respectively.
II. Entomophagous insects :
11.1. Predators :
Eight predaceous species were concerned in this study.
1.1. Orius spp.
The two Summer seasons study indicated that Orius: spp were
nearly of the same trend of occurrence in the two seasons.
Two peaks of the predator abundance of 118 & 98 adults / 50 plants
occurred on July, 29 th and August 19 th Summer plantation 1995. and 175
& 115 adults / 50 plants on August, 10 th, 31 st in Summer plantationl996.
The total number of counted adults was higher in the latter year (646 adults)
than in the former one ( 585 adults) .
As for the two NiH plantations, the predator was detected
throughout a longer period in 1996 than in 1995. Also higher total number of
Orius spp. adults were counted in 1996 (726 adults) than throughout 1995
( 636 adults) . Two peaks of the predator abundance each of 100 adults / 50
plants were detected on Sept., 9 th and Oct., 7 th . While 1996 in NiH
season, only one high peak of 17 adults / 50 plants were counted on August,
25 th. In the two seasons the existance of Orius coincidence with eggmasses
and young larvae of S.cretica & O.nubilalis and with S.Uttoralis
and S.exigua: and covered all the activity period of R. maidis
1.2. Scymnus spp. ( mainly inte”uptus Goeze and syriacus Mars. )
In Summer plantation 1995, this groups of predators was found highly
abundent from July, 22nd to August, 19 th and 28 adults were counted in
the last inspection, seemed to cover the activity period of the aphid
R.maidis. In 1996 Summer plantation, two peaks of abundance were
observed. The first was on August, 17 th with 70 adults in coincidence with
peak of R.maidis while the second on Sept., 7 th with 23 adults in absence
of R. maidis .
ill Nili plantation 1995, there was one peak of 34 adults on Sept., 23
th . While in 1996 Nili plantation there were three peaks on August, 25 th ,
Sept., 22 th and Oct., 20 th with 24 , 18 and 24 adults, respectively. In the
three peaks of activity Scymnus were in association with R.maidis .
1.3. Ladybird beetles.
1.3.a. Coccinella undecimpunctata L.
ill 1995 Summer plantation the predator appeared in high
abundance from August, 12 th to September, 2 nd where one peak of 170
individuals was detected on August 19 thoThe same trend of the predator
activity was observeds in 1996 Summer plantation where the predator
showed one peak of 320 individual on August, 17 th .
In 1995 Nili plantation, the predator started to appear from August, 5 th
up to October 14 th . Highest abundance of the predator 90 individuals
occurred on August, 26 th . In the subsequent Nili season, the peak of
predator abundance (274 individuals) was detected on August, 25 th 1996.
In the two seasons the predator seemed to be active against egg-masses and
young larvae of com-borers, S.littoralis, Sexigua and Lmaidis.
1.3.b. Cydonia vicina var. nilotica Muls .
One peak of the predator abundance of 38 adults I 50 plants was
the only detected in the Summer ( on August, 19 th ) and the Nili ( on
September,30th) season of the first year of study. While, in 1996, the
weeklycmmtsthroughout the period of both the Summer and Nili
plantations, were very weak. During the 2 seasons of study the predator
seemed to be active against R.1tUlidis .
1.3.c. Cydoniavkina var. isis Muls.
During the first Summer plantation, one peak of abundance (36
individuals) was detected on August, 19 th . While in 1996 Summer
plantation the predator showed its highest number ( 16 individuals) on
August, 17 th
In the first Nili maize plantation, the predator showed its peak of
abundance ( 36 individuals) on Sept., 30 th . While in 1996 Nili plantation,
the predator showed one peak of28 individuals on August, 25 th . On all
plantations aphids seemed to be the main prey of the predator.
1.3 .d. Adonia variegata Goez.
This predators was only observed in late summer and Nili
plantations! season 1996. Very few numbers could be detected feeding on
com aphids
1.4. Aphid lions Chrysoperla carnea (Steph. )
On maize plants of 1995 Summer season highest counts of larvae
were detected on August, 2 nd ( 36 larvae ). While in the subsequent
Summer season one peak of 33 larvae was detected on August, 17 th . On
NiH plantation, one peakof 16 larvae was detected on Sept., 30 th 1995.
While in 1996 NiH season, the predator larvae were detected throughout a
longer period but in few numbers.
1.5. Paederas alffierii . Koch
In Summer plantation 1995, adults were detected active during the
whole season representing a peak of 52 adults on mid July. In summer
plantation 1996, peak of 57 adults appeared on Sept., 7 tho .
InNiliplantation 1995, the predator was observed active from
August, 5 th..to the end of the season and reached its highest number 90
adults on Sept, 30 tho . The peak of 46 adults on Sept., 1st Nili plantation
1996 was noticed.
11.2.Parasitoids
IT.2.t. Egg parasitoid.
2.I.a. Platytelenomus hylas Nixon
It is an egg parasitoid on S.cretica . In both Summer seasons
.throughout the period that extended from August, 19 th up to the end of
1995 season the percentages ofparasitism ranged from 96.1-100 % an~
throughout the period from August, 24 th to the end of 1996 season,
parasitism occurred in 90-100 % of the host eggs. While in the Nili season
throughout the periods from August, 11 th to October 6 th 1996 the
percentages of parasitism ranged between 21.2 - 100 and 28.6 - 100 %
respectively.
2.I.b. Trichogramma evanscens Westwood
The percentages of parasitism byJ: evanscens were estimated in
O.nubilalis eggs infesting maize plants throughout 4 seasons of study. The
highest percentages of parasitism reached 55.85 % on Sept., 16 th and 52.94
% on sept., 21 st 1996 . On the Nili seasons, the highest percentages of
parasitism were recorded during the first week October 55.94 % 1995 and
the end of August (56.8 %) 1996.
II.2.2. Larval and pupal parasitoids:
2.2.a. Larval and pupal parasitoids of s.cretica weekly numbers
S.cretica larvae and pupae were collected from host plants during the two
successive years 1995 and 1996 . Six parasitoids species are recorded.
1. Meteorus rubensNees (Hymenoptera: Braconidae).
It is a gregarious parasite seemed from the larvae of s.cretica and
recorded during July in Summer plantation 1995 and 1996 _The rate of
parasitism ranged from 1.79 to 3.33 %.
2. Meteorus gyrator Thunberg (Hymenoptera: Braconidae)
It is a larval solitary endoparasitoid, M.gyrator was recorded during
summer plantation 1995 with rate of parasitism ranged from 2.1 to 3.7 %
3. Bracon brevlcornis Wesm. ( Hymenoptera: Braconidae ).
B. brevicornis is a gregarious ectoparasitoid recorded in the late of
season during Summer plantation 1996, with rate of parasitism ranged from
2.04 to 4 % . While in the two Nili plantations of 1995 and 1996 , the rates
of parasitism ranged from 2.86 to 3.33 % and 1.69 to 4.54 %, respectively.
4. Apanteles sp
Apanteles sp is a gregarious endoparasitoid. It was recorded only
during Summer plantation 1996 in July with a rate of parasitism ranged from
1.79 to 3.92 % .
5. Tachina larvarum ( L. ) ( Diptera : Tachinidae )
In Summer plantations 1995 and 1996, the rate of parasitism ranged
from 1.49 to 2.7 % and from 1.88 to 2.5 %, respectively. While those of
the two Nili plantations it ranged from 2 to 2.5 % and 1.88 to 2.7 %,
respectively .
6. Conomarium eremita Forst ( Hymenoptera: Pteromalidae )
C eremaa is a parasitic wasp recorded attacking the pupae of S.cretica
in the early season during Summer plantation of the two years . Overall
averages of parasitism were 1.21 % and 2.41 % during 1995 and 1996
respectively .
2.2.b. Larval parasitoid of O.nubilalis
Bracon brevicornis
B.brevicornis was recorded parasitizeing larvae of O.nubilalis
late in the season. In Summer plantation 1995 , the overall percentages of
parasitism were 1.2 % and 1.03 % in the Summer plantation, and 1.05 0,10
and 0.88 % in NiH seasons 1995 and 1996 respectively
2.2.c. Egg larval and larval parasitoids of S.littoralis and S.exigua :
1- Chelonus inanitus ( L. ) ( Hymenoptera: Braconidae )
Chelonus inanitus is an egg larval parasite . It was recorded
during July, August, September and early October in Summer and Nili
plantation Season 1995. The rate of parasitism ranged from 1.32 % on July,
29 th to 8.6 % on Sept., 9 th in Summer plantation 1995 . While in Nili
plantation it ranged from 0.61 % on Oct., 14 th to 5.88 % on Sept., 9 tho
2. Microplitis rujiventris Kok. (Hymenoptera: Braconidae)
M.rujiventris is an internal larval parasite was found attacking
both of S.litoralis and S.exigua larvae. In Summer plantation 1995 , the
percentages parasitism on S.litoralis larvae ranged from 4.65 %on July 8 th
to 17.73 % on August 19 th .while these percentages on S.exigua larvae
ranged from 4.76 o/OconJuly, 15 th to 10.41 % on July 1 st. In Summer
plantation 1996, the highest percentages of parasitism on S.littoralis larvae
was 13.33 %on July, 13 th while it was 4 % on S.exigua on July, 20 th .
In Nili plantation 1995, on S.littoralis larvae the rate of parasitism
ranged from 3.25 %on Oct., 28 th to 11.58 % on July 29 th . In Nili
plantation 1996, on 8.littoralis rate of parasitism ranged from 8.33 %on
Sept., 22 th to 17.85 %on Sept., 8 th . On the larvae of 8.exigua it was
4.76 % on July, 28 th
Zele nigricornis Walk. (Hymenoptera: Braconidae)
Z.nigricornis is an intemallarval parasite . It was found to be
attacking both S.litoralis and S.exigua larvae. In Summer plantation 1995 ,
the percentages of Z.nigricornis parasitism on S.litoralis larvae ranged from
0.9 % on July 22 th to 2.95 % on August 19 th,while these percentages
ranged from 2.94 % on July, 22 th to 4.76 % on July 8 th onS.exigua
larvae. In Summer plantation 1996, rate of parasitism on S.Uttoralis larvae
ranged from 2.17 % on July, 27 th to 3.03 % on July, 20 th .and from 3.13
% to 4.35 on July 20 & 13 th on S.exigua larvae.
In Nili plantation 1995, highest percentage of parasitism on
S.Uttoralis larvae was 1.41 % on August, 19 th . In Nili plantation 1996,
highest percentage of parasitism by Z.nigricornis on S.littoralis larvae was
4.34 % on Sept., 1 st and 4.76 % on S.exigua larvae on July, 28 th .
4. Apanteles.sp
Apantetes.sp is a parasitoid recorded also on larvae of
S.exigua in Summer plantation 1996 with a rate of parasitism ranged from
6.25 % on July, 20 th to 0.09 % on July 6 th.
5. Meteom« gyrator
M.gyratol’ parasitized S.exigua larvae with a rate of parasitism
ranged from 10 % on June, 24 th to 14.71 % on July, 22 th Summer
plantation 1995. While in Summer plantation 1996 the rate of parasitism
ranged from 5.25 % on July, 27 th to 8.69 % on July, 13 th . In Nili
plantations 1995 & 1996 highest rates of parasitism were 11.11 % on
August, 5 th and 4.76 %on July 28 th respectively.
6. Perlboeaorbtlta Wied (Diptera: Tachinidae)
P.orbata is an intemallarval parasite. It was found to be active
during July, August and September . In both of the two Summer plantations
1995 and 1996 the percentages of parasitism were ranged from 0.9 % on
July, 22 th to 3.94 % on August 19 th and from 1.88 %on August 3 rd to
3.23 % on August 24 th, respectively. In Nili plantations 1995 and 1996
percentages of parasitism ranged from 0.56 % on Oct., 7 th to 4.39 % on
Sept., 2 nd and from 4.16 % on August, 25 th to 5.26 on Sept., 15 !lh
respectively .
III. Percentages of parasitism by Bibrevicomis on larvae
of S.cretica and O.nubilalis infesting com stalks.
The rate of parasitism by B. brevicornis gradually increased as the
date of inspection advanced. On S.cretica,rates of parasitism ranged from
7.41 to 41.66 % and from 4.76 to 40 % during 1995 and 1996 seasons,
respectively .
OnO.nubilalis rate of parasitism ranged from 1.96 to 30 % and from
2.5 to 37.04 % during 1995 and 1996 season, respectively.
Sex-ratio of B. brevicornis :
Sex-ratio of Bibrevicomis could be detected by collected parasitized
larvae of O.nubilalis and S.cretica during the two successive years 1995 &
1996. The emerged parasite adults were obtained and differentiated into
females and males. indicating a sex ratio of 1 female ”:1.05 male and 1 :
1.09 incaseoflAnubilalis’ during 1995 and 1996 respectively. While in
case ofS.creticaa sex-ratio of 1 : 0.95 and 1 : 0.96 were obtained during
the two years respectively.
IV. Physiological studies on the haemolymph of both
active and hibernating heathy 6 th instar Sicretica and
O.nubilalis larvae and those parasitized by Bibrevicomis :
IV. I. Determination of total haemocyte counts (THCs).
After parasitization by the 2 nd instar of the braconid ectoparasitoid
Bracon brevicornis for both S.cretica and o.nubilalis larvae, a decrease in
the total haemocyte counts appeared as compared to those of unparasitized
ones during the active and diapausing period. Also a reduction in the total
haemocyte counts was observed during the diapausing period probably
reflected the very low metabolic activity in their physiological state.
IV.2. Types ofhaemocytes
On basis of light microscopy inspections, eight types ofhaemocytes
could be morphologically differentiated in the haemolymph of both s.cretica
and O.nubilalis. The identified haemocyte types were prohaemocytes,
phagocytic cells ( plasmatocytes, granular and spindle cells)
adipohaemocytes, oenocytoids cells, spherule cells and cystocyte cells.
Drawing and descriptions of the haemocytes are given.
IV.3. Differential haemocyte counts (DRCs) :
IV.3 .a. Qualitative analysis :
The sixth instar larvae of S.cretica and O.nubilalis just after
moulting were exposed to the females of the ectoparasite B.brevicornis.
Inspection of each of eight haemocyte types took place from host larvae, at
the third day of parasitism, where the parasitoid become in their 2 nd instar.
The haemolymph inspections included the dimensions of cells and nuclei
from each type (length and width) in unparasitized larvae as well as
parasitized ones of the same age during the active and diapausing period.
The nucleus cell ratio was also estimated in each case. Drawings of each
The nucleus cell ratio was also estimated in each case. Drawings of each
haemocyte type are given for the unparasitized and parasitized larvae
during the two periods.
Parasitism resulted in the appearance of abnormalities in all types of
haemocytes, as irregularity and elongation of cell wall with twisting it ends
of spindle cells. The cytoplasm of cells was badly and faintly stained.
During the hibernating period, the spherule cells of parasitized S.cretica
larvae disappeared from the haemolymph. Also, the cystocyte cells of
unparasitized O.nubilalis larvae were disapeared.
IV.3.b. Quantitative analysis ofhaemocytes :
The phagocytic cell ( plasmacytes, granular and spindle cells) in
parasitized larvae increased as compared to those of unparasitized ones of
the same ages while the prohaemocytes of parasitized larvae become
i reduced- in numbers-.as compared to those ofunparasitized larvae during the
active and diapausing period. The reduction in prohaemocytes is supposed
to be due to prohaemocytes transformation into phagocytic cells, which are
responsible for defence against invading organisms emphasizes their
function against the parasitoid. The spherulocytes and oenocytoids
decreased in parasitized larvae than in the unparasitized ones.
More, a decrease in numbers of all cell types was detected except
the adipohaemocytes which increased during the period of hibernation.
This probably correlated with the various physiological states of
hibernation development.