الفهرس 
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Abstract
Monitoring the changes in the population density and field generations of maize insect pests:
1-1- Sesamia cretica:-
For 2008 season, Two main period of activity were detected , the first effective brood from third week of March until last week of May and ineffective brood from last week of May until first week of October. The main peaks occurred at last week of May. While in 2009 season, the first effective brood was from third week of April until last week of May and ineffective brood from last week of May until first week of October. The main peak in both two years occurred at the second half of May. Four to five generations were observed
1- 2- Chilo agamemnon:-
C. agamemnon infested maize plants at the second half of May till the end of October in both two years 2008 and 2009. The main peak occurred at the second half of October. Four overlapping generations were observed.
1-3- Ostrinia nubilalis:-
The main period of O. nubilalis infestation in maize plants started at last week of August and continued until the first week of November during 2008 with main peak at last week of September. For 2009 season, the main period of occurrence was from the second week of August to last week of October with main peak occurred at third week of September. Three overlapping generations were detected in both two years.
1- 4- Rhopalosiphum maidis:-
During 2008, the largest size peak occurred on second week of August while in 2009, the largest peak occurred on last week of September.
1-5- Empoasca spp. :-
Empoasca spp. appears in maize fields for 2008 season at second half of April until the end of the season at first week of November. The main peak occurred at first week of June. For second season 2009, Empoasca spp. were first detected three weeks earlier than in 2008, at last week of March and continued until the first week of November. The main peak occurred on second week of June. Four field generations were observed during the activity period.
1-6- Nezara viridula :-
In both seasons during the activity period which extend from June to August.
1-7- pyroderces simplex:-
p. simplex larvae infested maize ears with scarcely low numbers during August and September for 2008 season while for 2009 season maize ears was free form p. simplex infestation.
1-8- Earias insulana:-
E. insulana occurred in few numbers on maize ears during maize growing season of 2008, while maize ears were free from E. insulana during the whole season of 2009.
2-The average percentages of corn borers and Rhopalosiphum maidis infestation throughout the maize growing season, March _ November in 2008 and 2009.
2-1- Sesamia cretica:-
The pattern of S. cretica infestation could be divided into heavy infestation (over 20%) during March, April and May, moderate (10-20%) during June, July and August and light (below 10%) during September and October.
2-2- Chilo agamemnon:-
For 2008 season, no infestation in maize plants were observed between March and May; moderate infestation (10-20%) from second half of May until first half of October and heavy infestation (over 20%) during 2nd half of October and 1st half of November. For 2009 season, C. agamemnon infestation could be divided into period of no infestation between March, April and second half of May, moderate infestation during second half of May until last week of August and heavy infestation during September and first half of October.
2-3-Ostrinia nubilalis:-
The main period of high infestation (over 30%) by this borer is fairly long extending for nearly two months between September and October. from the nature of this pest’s occurrence of infestation “durations” and “Categories” could be detected, period of no infestation from March to first half of August while light infestation (between 10-20%) occurred during second half of August.
2-4-Rhopalosiphum maidis:-
The highest level of infestation (over 20%) were detected during second half of August till first half of September in both two seasons and moderate infestation prevailed from second half of July until second week of August.
3-The fluctuations in corn borer’s and Rhopalosiphum maidis infestation in relation to planting dates:
3-1-First planting date (March plantation) :-
Maize plants sown on March harbored high level of S. cretica infestation (30-100%) and (20-80in 2008 and 2009 respectively. The average percentages of C. agamemnon infestation for 2008& 2009 seasons were varied between (10-50%) and (20-60%)) respectively. O. nubilalis was regarded as a secondary pest on maize plants sown at March while no infestation by R. maidis appeared in March plantation during 2008 and 2009 seasons.
3-2-Second planting date (April plantation) :-
Maize plants sown on April also harbored a high level of infestation by S. cretica (10-30%) during 2008 and (20-60%) during 2009. Sever infestation with that pest occurred on late July 2008. The average percentages of C. agamemnon infestation for 2008& 2009 seasons were For C. agamemnon, the average percentage of infestation was 10% during 2008 season, while for 2009 season it was (10-60%).
During 2008 season both O. nubilalis and R. maidis were secondary pests while for 2009 season maize plants were entirely free from O. nubilalis and R. maidis infestation.
3-3-Third planting date (May plantation) :-
The infestation % of S. cretica, C. agamemnon fluctuated within 10-30% and 10-60% respectively. No infestation by O. nubilalis was detected during 2008. R. maidis infestation occurred on maize plants of age between 67-107 days and fluctuated within 20-40%.
3-4-Forth planting date (June plantation) :-
For the first season 2008, the infestation % of Sesamia cretica ranged between (10% - 30%) while in 2009 infestation % ranged between (20-60%). For C. agamemnon infestation % varied from 10-40% and 40-60% in 2008 and 2009 respectively. During July plantation, maize plants were subject to high level of R. maidis infestation during 2008 &2009 seasons. infestation % varied between (10-90%) and (40% -80%) respectively.
3-5-Fifth planting date (July plantation) :-
S. cretica infestation% varied between (10-60%) for 2008 and (20-40%) for 2009. For C. agamemnon infestation% was 10-20 % during 2008 and 20-60 % during 2009. During July plantation, infestation% of O. nubilalis infestation varied between (30-80%) for 2008 while in 2009 season it fluctuated within 10-80%. For 2008 season, R. maidis average of infestation ranged between (20%-80%). For 2009 season, the average of infestation ranged between (20%-100%).
3-6-Sixth planting date (August plantation) :-
plantation date of August, maize plants harbored the lowest level of infestation by S. cretica and C. agamemnon while infestation by O. nubilalis ranged between 10-60%. This plantation harbored high level of R. maidis infestation, it ranged between 10-30% during 2008 while for 2009 season it was 20-80%.
4- Monitoring population dynamic of the main maize pests based on planting dates and the corresponding infestation levels.
4-1-Sesamia cretica:-
For both 2008 and 2009 seasons, results of statistical analysis showed the presence of significant differences between means of the population at different sowing dates. The highest number of S. cretica larvae was obtained on maize plants sown as early as March.
4-2- Chilo agamemnon:-
For the first season 2008, the analysis of variance yielded a significant ”F” value for the differences between the population densities of C. agamemnon larvae inhabiting maize plants sown on different planting dates. It seems that maize plants sown early on March were more liable to be attacked by C. agamemnon as compared to the other planting dates. For the second season (2009), results of statistical showed insignificant differences between means of larval contents.
4-3- Ostrinia nubilalis:-
For 2008 season analysis of variance of the data obtained showed significant differences between the mean numbers of O. nubilalis observed on the six tested maize planting dates. The highest mean numbers of O. nubilalis found on maize sown on July compared to maize sown on June, August, March and April respectively. On the other hand, maize plants sown on May were completely free of O. nubilalis infestation. For the second season (2009), the analysis of variance yielded significant ”F” value for the differences between the population densities of O. nubilalis larvae inhabiting maize plants sown on different planting dates. The highest mean number of O. nubilalis found on maize sown on June compared to maize sown on July, August, May and March respectively while maize plants sown on April was free from O. nubilalis infestation.
4-4- Rhopalosiphum maidis:-
Analysis of variance of the data obtained during the first season 2008 indicated the presence of significant differences between mean numbers of R. maidis observed on the tested maize planting dates. The highest number of aphid population was occurred for maize sown on June, followed by those sown on July, May, August and April. While maize plants sown on March were free from R. maidis infestation.
During 2009 season; analysis of variance of the data obtained showed insignificant differences between the mean numbers of R. maidis individuals. The highest number of aphid population was occurred for maize sown in August followed by July and June, while those sown in March, April and May were free of infestation.
5- Monitoring the accumulated growing thermal units needed for developmental maize when different maize planting dates are considered.
For first season 2008, planting dates of 11thMarch, 13thApril, 10thMay, 14thJune, 9th July and 12th August requires about 77, 75, 74, 58, 56 and 60 days from planting to tasseling, its receive an average of 930, 1025, 1121, 936, 916 and 943 DDs. For the second season 2009, planting dates of 6th March, 6th April , 6thMay, 6thJune, 6thJuly and 6thAugust requires about 124, 122, 116, 88, 94 and 91 days from planting to maturity, its receive an average of 1672, 1793, 1658, 1424, 1496 and 1319 GDDs .
For second season 2009, planting dates of March, April, May, June, July and August requires about 90, 76, 68, 58, 63 and 55 days from planting to tasseling, its receiving an average of 918, 947, 988, 934, 1010 and 846 GDDs while it requires about 136, 121, 106, 93, 93 and 98 days from planting to maturity, its receive an average of 1649, 1682, 1608, 1481, 1458 and 1441GDDs.
6- The relation ship between maize phonological stages and the corresponding main insect pest’s infestation in the different planting dates.
6-1- First planting date ”March planting”:-
6-1-1-Sesamia cretica:- For both 2008 and 2009 seasons, maize plants were subject to heavy infestation by S. cretica larvae from last week of April till forth week of May during vegetative stages before “tasseling”, while low infestation was recorded through maize reproductive stages.
6-1-2-Chilo agamemnon:- For both 2008 and 2009 seasons maize plants were subject to higher level of C. agamemnon infestation during reproductive stages.
6-1-3-Ostrinia nubilalis:- Numbers of Ostrinia nubilalis larvae were relatively low in both 2008 and 2009 seasons.
6-1-4- Rhopalosiphum maidis:-Maize plants were from R. maidis infestations during 2008 and 2009 seasons.
6-2-Second planting date ”April planting”:-
6-2-1-Sesamia cretica:- For both seasons 2008 and 2009, the infestation by S. cretica was first recorded at (L2 & L6 stages) and continued until reproductive stages (dent & dough stage). Low level of S. cretica infestation was observed during reproductive stages.
6-2-2-Chilo agamemnon:- For 2008 season, C. agamemnon larvae show up in few numbers about second week July after silk stage and continued until dent stage. For 2009 season, C. agamemnon infested maize plants as from third week of May ”L8 stage” till ”dough stage” .
6-2-3-Ostrinia nubilalis:-For 2008 season, O. nubilalis appeared as a secondary maize pest while for 2009 season; this borer pest wasn’t observed in April plantation,
6-2-4- Rhopalosiphum maidis:- Infestation by R. maidis did not show up, altogether, during 2009 season , and was absent in the majority of the examination in 2008 season. The infestation by R. maidis was only detected for 2008 season at last week of June during ”tasseling period”.
6-3-Third planting date ”May planting”:-
6-3-1-Sesamia cretica:- Larvae of S. cretica had first observed during last week of May in 2008 at L8 stage continued until dent stage. For 2009 season, S. cretica had first detected at L4 stage and continued until the L17 stage while it did not appeared at reproductive stages. In both years, the larval content fluctuated within a range of low and moderate level of infestation
6-3-2-Chilo agamemnon:- During 2008 season; larvae of C. agamemnon had observed from L11 stage and continued till dent stage in while for 2009 season, shorter period of C. agamemnon infestation were recorded from L8 stage and continued until L16 stage.
6-3-3-Ostrinia nubilalis:- In May plantation, O. nubilalis appeared as a minor pest in 2009 maize season but could not be detected altogether in 2008 season.
6-3-4- Rhopalosiphum maidis:-For 2008 season, the main period of R. maidis infestation on maize plants occurred a week earlier before tasseling stage at third week of July and continued till dough stage, Low level of R. maidis infestation was observed in this season. For 2009 season, maize plants were free from R. maidis infestation.
6-4-Forth planting date ”June planting”:-
6-4-1-Sesamia cretica:- For 2008 season 2008 season, S. cretica was first recorded in maize plants by first week of July (L8 stage) and continued till dent stage. For 2009 the infestation by S. cretica was first discovered at first week of July (L9 stage) and disappeared at milk stage. Maize plants were subject to high level of S. cretica infestation in the period from L10 to L12 stage.
6-4-2-Chilo agamemnon:-C. agamemnon larvae infested maize plants at last week of August during milk stage and continued till dent stage during 2008 season. For 2009 season the main period of C. agamemnon infestation was from first week of August during tasseling stage and lasted till dent stage with a high level of infestation.
6-4-3-Ostrinia nubilalis:-For 2008 season, infestation by O. nubilalis larvae was first detected at last week of August (milk stage) and continued till the second week of September (dent stage). In 2009 O. nubilalis infestation started two weeks earlier than in 2008 at blister stage and continued till dent stage, the average level of infestation was high in both years.
6-4-4-Rhopalosiphum maidis:- Corn leaf aphid had first observed during forth week of July in 2008 at L11 stage continued until dent stage. For 2009 season, R. maidis had first detected at L14 stage and continued until milk stage. High numbers of R. maidis individuals infested maize plants during tasseling and silking stage during both 2008 and 2009 seasons. Nymphs and adults appears in colonies on the upper leaves and tassels,
6-5-Fifth planting date ”July planting”:-
6-5-1-Sesamia cretica:- S. cretica attacked maize plants with moderate rate of infestation in 2008 season at (L8 stage) earlier than 2009 season (L9 stage) and continued in few numbers till dent stage .
6-5-2-Chilo agamemnon:- C. agamemnon started infesting maize plants of 2009 season at a comparatively earlier stage (L15 stage) when compared with 2008 season (milk stage) and continued till dent stage in both seasons.
6-5-3-Ostrinia nubilalis:-For both seasons 2008 and 2009, larvae of O. nubilalis were found on first week of September (tasseling stage) and continued till dent stage. O. nubilalis represented by high rate of infestation during 2008 and 2009 seasons.
6-5-4-Rhopalosiphum maidis:- During 2008, the initial R. maidis infestation started in this plantation at first week of August L14 stage until dent stage. For 2009 season, R. maidis was first detected at last week of August at L15 stage and continued till dough stage. The maximum rate of R. maidis infestation was during tasseling stage.
6-6-Sixth planting date ”August planting”:-
6-6-1-Sesamia cretica:- In 2008, practically no infestation other than a minor one detected at second half of September, when plants were at L12-L14 stage. No S. cretica infestation appeared in 2009 but a single one took place on first week of August (L3 stage).
6-6-2-Chilo agamemnon:- By the end of this sixth plantation in 2008 season, a few numbers of C. agamemnon larvae were found in the examined plants “milk stage”, while for 2009 season C. agamemnon infestation took place at last week of September “ tasseling stage” till milk stage .
6-6-3-Ostrinia nubilalis: For 2008 seasons, O. nubilalis infested maize plants at L11 stage then it disappeared and show up again at tasseling stage and continued till dough stage, while for 2009 season, high level of O. nubilalis infestation was detected at dent stage.
6-6-4-Rhopalosiphum maidis:- For both 2008 and 2009 seasons, the maximum number R. maidis individuals were detected during tasseling stage.
7-The age of maize plants at which initial and maximum insect pest infestation occur.
Initial infestation of S. cretica, C. agamemnon, O. nubilalis and R. maidis occurred when plant age was (23-59-64-52 days plants old respectively).
Maximum infestation of S. cretica, C. agamemnon, O. nubilalis and R. maidis occurred when plant age was (49-80-74- 65 days plants old respectively).
8- Monitoring the changes in the population density of some natural enemies inhabiting maize fields.
It could be concluded that the main period of (paederus alfierii, coccinellid spp and Chrysoperla carnea) the main predators inhabiting maize field were during the period extending between April to July for paederus alfierii, March to May for Chrysoperla carnea and from March to August for coccinellid spp
9- Evaluating the role of natural enemies governing the changes in the population density of maize insect pests.
9-1- Sesamia cretica:-
The changes in the population densities between S. cretica larvae and p. alfierii were negatively insignificant for both 2008 and 2009 seasons. While it was positive insignificant between S. cretica larvae and coccinellid spp. during both 2008 and 2009 seasons and significant positive with Chrysoperla carnea during 2008 but positive insignificant during 2009.
9-2- Chilo agamemnon:-.
The estimated correlation coefficient values between C. agamemnon and p. alfierii were positive and significant during 2008 and negatively insignificant for 2009 season. For C. agamemnon and Coccinella spp. combined negative and insignificant relationship was observed during both 2008 and 2009 seasons. The estimated correlation coefficient values between C. agamemnon individuals and C. carnea eggs was negative and insignificant during 2008 and 2009 seasons,
9-3- Ostrinia nubilalis:-
The estimated correlation coefficient values for the relation between O. nubilalis and p. alfierii appeared to be negative and insignificant during 2008 and 2009 seasons, negative insignificant with coccinellid spp. and negative insignificant with C. carnea eggs during both 2008 and 2009 seasons.
9-4- Rhopalosiphum maidis:-
The correlation coefficient values between R. maidis and the corresponding number of p. alfierii were negative insignificant for both 2008 &2009 seasons, negative insignificant with Coccinella spp. during 2008 &2009 seasons while it was negative insignificant with C. carnea .
10-Effect of some weather factors on the population density of maize insect pests:
10-A- Sesamia cretica:-
For day maximum temperature: The correlation coefficient ”r” -0.28 and -0.42 was negative insignificant for both 2008 and 2009 seasons respectively.
For day minimum temperature: The correlation coefficient ”r” -0.47 & -0.63 was negatively insignificant during 2008 and negatively significant 2009 seasons.
For relative humidity (RH%):The estimated correlation coefficient ”r” -0.42 and -0.55 values were negatively insignificant for 2008 seasons and negatively significant for 2009 season.
The combined effect of the three weather factors: The percentage of variance explained by the three tested weather factors combined was statistically insignificant for 2008 (29%) but significant for 2009 seasons (55 %).
10-B- Chilo agamemnon:
The correlation coefficient values ”r” -0.30 and -0.53 For day maximum temperature were negatively insignificant during 2008 but negatively significant during 2009 season.
For day minimum temperature: The correlation coefficient ”r” values were -0.32 and -0.17 were negatively insignificant during both 2008 and 2009 seasons.
The correlation coefficient ”r” 0.0001 for RH % was negative and insignificant during 2008 season and positive and insignificant for 2009 season (0.47).
The combined effect of the three weather factors: The amount of variance in the seasonal activity explained by three tested weather factors combined was (11% and 42%) during 2008 and 2009 seasons.
10-C- Ostrinia nubilalis :-
The correlation coefficient values (r) for day maximum temperature were 0.20 for the first season and 0.62 for the second season; these values were positively insignificant for 2008 season and positively significant for 2009 season.
For daily minimum temperature simple correlation ”r” values were positively insignificant for both 2008 (”r”= 0.31) and 2009 seasons (”r” 0.490).
For RH% simple correlation ”r” values were negatively insignificant during 2008 (-0.08) and negatively significant for 2009 season (-0.80).
The amount of variance for the seasonal activity explained by three tested weather factors combined was 19% for 2008 and 65 % for 2009.
10-D- Rhopalosiphum maidis :
For day maximum temperature correlation coefficient values yielded positively insignificant for 2008 season (”r”= 0.18) and negatively insignificant for 2009 season (”r”=-0.29).
The simple correlation coefficient values were positively insignificant during 2008 (”r”= 0.40) for day minimum temperature but negatively significant for 2009 season (”r”=-0.56).
For (RH %): The correlation coefficient ”r” values were -0.01 and -0.30 negatively insignificant for both 2008 and 2009 seasons.
The amount of variability in the seasonal activity explained by three tested weather factors combined was (43 % and 32 %) during 2008 & 2009 seasons.
11-The Effect of different planting dates on maize yield.
Maize plants sown on June, March, May and April had the highest average kernel weight per plant (171.0, 170.0, 149.9 and 139.3 gm respectively), compared with maize plants sown during July and August (104.0, 99.8 gm respectively). For the second season 2009, Delayed in maize planting date reduced average kernel weight. Maize sown on July and August yielded the lowest kernel weight per maize plant (101 and 98 gm respectively) as compared with that of April, March, May and June (269.2, 244.0, 201.3 and 163.5 gm respectively).
12-The simultaneous effect of Sesamia cretica, Chilo agamemnon, Ostrinia nubilalis, and Rhopalosiphum maidis infestation on the maize yield.
The effect of S. cretica in 2008 and 2009 was significantly positive indicating that increases of 1% in the average infestation by this borer from one planting date to the next increase the average weight of maize ear by 0.93 gm and 5.59 gm respectively.
In 2008 season, the effect of C. agamemnon was significantly positive (6.34) indicating that increases of 1% in the average infestation by C .agamemnon from one planting date to the next increase the average weight of maize ear by 6.34 gm while for 2009 season, the effect of C. agamemnon on average kernel weight was negatively insignificant, the correlation coefficient ”r” values were -0.22.
The corresponding damage of O. nubilalis indicating that an increase of 1% in the average infestation by this borer from one planting date to the next decrease the average weight of maize ears by 5.93 gm in 2009 seasons while the correlation coefficient ”r” values were -0.48 negatively insignificant for 2008 season.
The increases of 1% in the average infestation by R. maidis from one planting date to the next decrease the average weight of maize ear by 3.71gm for 2009 seasons while the correlation coefficient ”r” values were -0.27 negatively insignificant for 2008 season.
The total variance explained by the effect of the four maize insect pests (S. cretica, C. agamemnon, O. nubilalis and R. maidis) combined on the average ear weight per plant of the six plantations ranged between 75% in 2008 and 97%.