الفهرس 
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Abstract
Ornamental plants considered as an important plants because they add a sense of beauty and enjoy natural joy of life. The problem that facing their production is the devastation of insect pests attacking these plants. Coccoidea pests are the most important pests as key pests and standing obstacles in either the expansion of their cultivation or the increase of their production. The studies have been carried out to explain the population dynamics and distribution of these coccoids on certain hosts of the ornamental plants, under the condition of middle Egypt. The experimental work was carried out in the Agricultural Experimental Station of the Faculty of Agriculture, Assiut University, during the two successive seasons of 2008/2009 and 2009/2010. The studied cocoidea insects represent the three groups of the super family as follow:
1- Hard scale insects: represented by the black scale insect, Chrysomphalus ficus Ashmead.
2- Soft scale insects: represented by the black olive scale insect, Saissetia oleae (Olivier).
3- Mealybugs: represented by the long-tailed mealybug, Pseudococcus longispinus (Targioni-Tozzetti).
The obtained results from this investigation was summarized in the following points
1. Simple description of the studied coccoidea pests, their damage and their parasitoids.
A simple description either for the studied pests, their damage and their parasitoids can help both the reader and the specialist to understand the subject from the destination he wants.
2. Population studies:
The population studies included the population dynamics within- time and the population distribution within- plants.
2.1. The black scale insect, C. ficus Ashmead :
2.1.1. Population dynamics:
2.1.1.1. Seasonal abundance:
Data of both seasons clearly indicated that the pest population was concentrated during the period from December to April. At this period, 68.92 ad 73.38% of the pest population was recorded during the 1st and 2nd seasons. The highest percentage of the pest population was recorded during February of the 1st season (15.96%) and during April of the 2nd one (16.16%). The period from June to September contained the lowest percentages (6.16 and 2.34%) of the pest population during both seasons, respectively. August contained the lowest population numbers during both seasons.
2.1.1.2. Number of annual field generations:
There are four field generations were obtained during each season under Assiut district conditions.
During the first season, these generations were from October,15 to December, 24; December, 31 to April, 22; April, 29 to June, 3 and June, 10 to September, 30 for the 1st, 2nd, 3rd and 4th generations, respectively. These generations lasted 70, 113, 36 and 112 days, respectively.
During the second season, these generations were from October,7to December, 17; December, 24 to April, 15; April, 22 to May, 20 and May, 27 to September, 30 for the 1st, 2nd, 3rd and 4th generations, respectively. They lasted 71, 113, 28 and 126 days, respectively.
2.1.1.3. Monthly Variation Rate (M.V.R.):
Results of both seasons, showed that the optimal and favorable period for insect population growth was found to be during September. The relative favorable periods occurred during the periods from September to March (temperature ranged from 13.89 to 29.19ºC and relative humidity ranged from 46.52 to 59.81%).
2.1.1.4. Factors affecting the black scale insect population:
2.1.1.4.1. The parasitoid Aphytis lingnanensis Compere (Hymenoptera:Aphelinidae):
The survey of C. ficus parasitoids revealed to one parasitoid species during the both seasons under Assiut district conditions.
Results showed that the highest weekly counts of the parasitoid population were 490 individuals/150 leaves and 559 individuals/150 leaves on the last week of January of the first and the second season. Only 1 individual/150 leaves of this parasitoid was recorded during the 2nd and 4th week of August of the first season and did not recorded at all during the same period of the second season. The percentages of parasitism ranged from 2.98 on August to 6.35% on November and 3.70 on April to 5.00% on August and September of the first and the second season, respectively.
Data of both seasons concerning the effects of weather elements on the parasitoid population revealed clearly that the changeable weather element which responsible for the most changes in A. lingnanensis population was minimum temperature, whereas, maximum temperature and relative humidity changed their sites from season to another.
2.1.1.4.2. Weather elements:
Data of the two seasons revealed that the most effective weather variables were the minimum temperature and relative humidity during the first season, and the minimum and maximum temperature during the second season.
2.1.2. Population distribution:
The population distribution of C. ficus on H. helix plants was studied and the obtained results showed that:
Concerning the leaves level (heights), the percentages of the black scale insect population on bottom, middle and top levels were 53.40, 32.48 and 13.76%, and 44.82, 33.44 and 21.74% during 2008/2009 and 2009/2010 seasons, respectively.
Concerning the branches levels (heights), the percentages of C. ficus population on the bottom, middle and top levels were 55.68, 31.98 and 12.34%, and 45.18, 33.99 and 20.84% during the tow successive seasons, respectively.
Concerning the leaf surface, the percentages of the pest population on the upper and lower surfaces were 64.18 and 35.82% during the first season and 59.54 and 40.46% during the second season.
Concerning the plant parts, the pest population was more abundant on leaves than that on branches during both seasons. The percentages of pest population on H. helix leaves and branches were 69.96 and 30.04% during 2008/2009 season, and 69.08 and 30.92% during 2009/2010 season.
2.2. The black olive scale, S. oleae (Qlivier)
2.2.1. Population dynamics:
2.2.1.1 Seasonal abundance:
It is clear that, during both seasons, the population of the black olive scale insect reached its highest levels after July (August and September). The lowest population was recorded during the period from February to April and from January to April during the 1st and 2nd seasons. The pest population on the 1st season was higher than that on the 2nd one.
The highest percentages of the pest population were occurred on August (23.59%) and September (23.49%) of the first season and September (27.17%) and August (26.18%) of the second season.
2.2.1.2. Number of annual field generations:
Results of both seasons revealed to the occurrence of five generations for S. oleae on N. oleander leaves at Assiut region. The longest generation was the 3rd one where the temperature was in its lowest level during the period of this generation.
2.2.1.3. Monthly Variation Rate (M.V.R.):
Obtained results showed that the favorable periods for the insect were from May to August of the first season and March to September of the second season. Climatic conditions of April were the optimal for the insect multiplication and build up, since the highest M.V. R. value was achieved during both seasons.
2.2.1.4. Factors affecting the black olive scale insect population:
2.2.1.4.1. Weather elements:
It could be concluded from the obtained results, that the efficiencies of minimum temperature, relative humidity and maximum temperature on the pest population changes were 56.55, 17.59 and 0.034%, and 53.89, 13.21 and 0.001% during the first and second seasons, respectively.
2.2.2. Population distribution:
Results of both seasons which dealt with the population distribution of S. oleae within oleander plant can be summarized in the following points:
Concerning the leaves heights, the percentages of the insect population on the bottom, middle and top levels were 45.17, 32.73 and 22.10%, and 44.36, 32.90 and 22.74% during 2008/2009 and 2009/2010 seasons, respectively.
Concerning the branches heights, the percentages of S. oleae population on the bottom, middle and top levels were 45.55, 32.91 and 21.54%, and 42.24, 30.46 and 27.30% during the first and the second seasons, respectively.
Concerning the leaf surface, the percentages of the pest population on the lower and upper leaf surfaces were 56.06 and 43.94% during the first season and the same exact percentages were occurred during the second one.
Concerning the plant parts, the pest population was more, in general, abundant on leaves than that on branches during both seasons. It was 61.67 and 38.33% during the first season and also approximately the same 60.51 and 39.49% during the second season on leaves and braches.
2.3. The long-tailed mealybug, Pseudococcus longispinus (Targioni-Tozzetti).
2.3.1. Population dynamics
2.3.1.1. Seasonal abundance:
Results of the weekly counts showed that the population of the insect during the first season reached its highest level during the last week of August for nymphs (18094 individuals/150 leaves) and during the 1st week of September for adults (4585 individuals/150 leaves), while the lowest level of the weekly count was recorded during the 1st week of March (10 and 359 individuals/150 leaves) for nymphs and adults. The highest percentage of the total mean monthly count was recorded on August (30.51%) followed by (28.47%) on September. The percentages of the total mean monthly counts from December to May ranged from 0.18 to 1.73%of the total year count.
During the second season, the highest weekly count was recorded during the 2nd and the 3rd week of August (4020 and 16575 individuals/150 leaves) for adults and nymphs, while the lowest weekly count was observed during the 1st week of February (9 and 17 individuals/150 leaves for nymphs and adults). The highest percentage of the total mean monthly count was recorded on August (30.65% of the total season count) followed by July and September, which were approximately the same (21.36 and 20.81%), while during the months from December to April, these percentages ranged from .09 to 0.86%of the total year count.
Data of both seasons, revealed that the highest weekly population was counted during the 3rd week of August. Also, the highest percentage of the total mean mean monthly count was recorded during the same month.
2.3.1.2 Number of annual field generations:
Four generations were recorded during each of both seasons. During the first season, the 1st generation was from October, 15 to November, 26 and lasted 42 days. The 2nd generation was from December, 3 to May, 20 and lasted 158 days. The 3rd generation was from May, 27 to June, 24 and lasted 28 days. The last generation which was the 4th one from July, 1 to September, 30 and lasted 91 days.
During the second season, the 1st generation was from October, 7 to November, 26 and lasted 48 days. The 2nd generation was from December, 3 to April, 29 and lasted about 147 days. The 3rd generation was from May, 6 to June, 10 and lasted 35 days. The last generation which was the 4th one lasted about 105 days and started from June, 17 to September, 30.
The results, of both seasons, show that the longest generation was the winter-spring generation and the shortest one was the summer generation because of temperature.
2.3.1.3. Monthly Variation Rate (M.V.R.):
Generally, the most favorable months for the insect multiplication were April, May, June and July during the first season and March, April, May and June during the second season. The optimal month for the population growth and build up found to be on April (23.58ºC and 42.17% R.H.) during the first season and May (28.18ºC and 35.45% R.H.) during the second one.
2.3.1.4. Factors affecting the long-tailed mealybug population:
2.3.1.4.1. The parasitoid , Coccidoxenoides perminutus Girault (Hymenoptera: Encyrtidae):
There is only one parasitoid species and a first record of Egypt attacking the long-tailed mealybug during both seasons. Concerning the weekly count of this parasitoid, the highest population was recorded on the 1st week of September (325 individuals/150 leaves and the 3rd week of August (284 individuals/150 leaves) during the first and the second seasons, respectively. The lowest population was observed on the last week of January and 2nd week of February (3 individuals/150 leaves each) during the first season, and it was not found at all in the field from January, 21 to February, 4 during the second season.
The percentages of parasitism ranged from 0.001 on January to 0.06 on March during the first season and ranged from 0.007 on January to 0.05 on March during the second season.
Multiple regression analysis showed that most of the changes in its population were due to minimum temperature followed by relative humidity and maximum temperature during both seasons.
2.3.1.4.2. Weather elements:
from the obtained results of both seasons, revealed that the minimum temperature was the major element influencing the changes of the long-tailed mealybug population. The efficiencies of minimum temperature in the pest population changes were 55.16 and 59.59 during the first and second seasons.
2.3.2. Population distribution:
The distribution of the insect pest population on A. marginata plants was studied from several faces and the obtained results can be summarized as follow:
Concerning the leaves level, the percentages of the insect population on bottom, middle and top levels were 43.16, 31.90 and 24.93%, and 41.14, 33.07 and 25.78% during 2008/2009 and 2009/2010 seasons, respectively.
Concerning the branches levels (heights), the percentages of P. longispinus population on the bottom, middle and top levels were 39.88, 34.11 and 26.01%, and 40.98, 33.21 and 25.81% during the first and the second seasons, respectively.
Concerning the leaf surface, the percentage of the pest population on the lower surface was higher than that on the upper surface. It was 56.88 and 43.12% during the first season and 55.63 and 44.37% during the second one on lower and upper surfaces, respectively.
Concerning the plant parts, the population of this Coccoidea pest was more abundant on leaves than that on branches during both seasons. It was 68.19 and 31.81% during 2008/2009 season and 68.09 and 31.91% during 2009/2010 season on leaves and branches, respectively.
3. Susceptibility of long-tailed mealybug, Pseudococcus longispinus to the tested entomophathogenic fungi.
The increase public awareness and concern for the environmental safety has directed research to alternative control strategies, other than use of pesticides. The use of entomopathogenic fungi is among the most promising alternatives, since they combine low mammalian toxicity, high effectiveness, and natural origin.
3.1. Susceptibility of P. longispinus to Beaveria bassiana:
Regarding the susceptibility of P. longispinus adults to B. bassiana, the difference between LT50 for the insects treated with the highest concentration and the lowest one was only 1.647 day. While in the case of nymphal stage, the difference between the highest and lowest concentration was 1.79 day .The results of the present study showed that the toxicity of B. bassiana on P. longispinus adults was nearly the same toxicity on the third nymphal stage. Slope values were relatively higher in the adult stage compared with nymphal one.
3.2. Susceptibility of P. longispinus to Metarhizium anisopliae:
The differences between the time required to kill 50% of insects treated with the highest and lowest concentrations of M. anisopliae were 2.1 and 1.55 day for the adults and nymphs, respectively.
Values of LC50 of both fungi species on the adults stage were almost the same. The difference between LC50 of B. bassiana and M. anisopliae on the nymphal stage was less than two fold. Both adult and nymphal stages showed nearly the same susceptibility toward the both species of fungi. All slope values of the toxicity lines were low.