الفهرس 
INTRODUCTION
Survey of insect species in sorghum fieldsOnly 14 pages are availabe for public view
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Abstract
1-Effect of the tested insecticides on the population density of R. maidis on Horus and Dorado plants in 2009 season.:-
The relative toxicity of acetamiprid, imidacloprid, spinosad, chlorpyrifos and cypermethrin were tested against the aphids population at Faculty of Agriculture AL-Azhar University Assiute during 2009 sorghum seasons. The aphids population were counted before insecticide application and after insecticide application. Insecticides were applied after the appearance nymph in the field during year of study 2009.
In Horus and Dorado plants, The populations of aphid was strongly decreased in all treated plots after 3 days of treatment compared with control. Treatment with imidacloprid, acetamiprid and spinosad proved to be more effective against R. maidis as Chlorpyrifos and cypermethrin were less effective representing. The efficacy of all tested insecticides after 17 days from spraying in reducing aphids. percent reduction for imidacloprid, acetamiprid, spinosad, chlorpyrifos and cypermethrin, respectively. The egg and nymph populations in all the plots, including control were reduced after 37 days from application representing reduction percent for imidacloprid, acetamiprid, spinosad, chlorpyrifos and cypermethrin, respectively
Effect of the tested insecticides on the population density of Sesamia cretica on Horus and Dorado plants in 2009 season:-
In Horus and Dorado plants, the population of Sesamia cretica was significantly decreased in all treated plots after 3 day of application in comparison to control. Treatment cypermethrin, chlorpyrifos and spinosad proved to be most effective against S. cretica. Next in order of efficacy were imidacloprid and acetamiprid and showed intermediate affected on S. cretica respectively.The efficacy of all the insecticides after 17 days of spraying was decreased, though significantly higher than the control. cypermethrin was again highly effective followed by chlorpyrifos, spinosad, Imidacloprid and acetamiprid.
The eggs and larvae population in all the plots, including control were reduced after 37 days of application insecticides. Maximum level of control was achieved by cypermethrin among all the insecticide after 37 days of spraying. Followed by acetamiprid. while chlorpyrifos, spinosad, imidacloprid were insignificant them.
2. Reduction in beneficial arthropods in sorghum fields treated tested compounds and their selectivity in sorghum ecosystem.
Application of pesticides in agro ecosystem is most commonly factor that causes the most direct reduction in arthropod natural enemies of pests in this system. These effects have been demonstrated by resurgences of target pests and the changes in status, of formerly economically unimportant species into important pests. Thus this investigation was made to study the effect of tested compounds on beneficial arthropods population.
A.Effect of the tested insecticides on the population density of C. undeciumpunctata on Horus and Dorado plants in 2009 season.
In Horus and Dorado plants, the population larvae and adults of density C. undeciumpunctata were insignificantly varied from plants in all the treatments before application of insecticides in the year 2009. The tested compounds did not completely eliminate with the beneficial arthropods. The larvae and adults population were significantly decreased in all treated plots after 3 day of application insecticides in comparison to control. The arrangement pesticides according to high percent reduction were cypermethrin and chlorpyrifos and insignificantly between acetamiprid and spinosad, and the lowest imidacloprid, respectively after 3 day. Minimum level of reduction was achieved by imidacloprid among all the insecticide after 17 days of spraying, followed by acetamiprid, spinosad, chlorpyrifos and cypermethrin respectively. The percent reduction of all the insecticides after 37 days of spraying was increased. midacloprid was again the lowest effective followed by acetamiprid, spinosad, chlorpyrifos and cypermethrin respectively. Degree of selectivity of imidacloprid and acetamiprid were good selective spinosad was selective, chlorpyrifos and cypermethrin was medium selective
B.Effect of the tested insecticides on the population density of Orius spp on Horus plants in 2009 season.
The population of density Orius spp on Horus plants were insignificantly varied from plants in all the treatments before application of insecticides in the year 2009. The tested compounds did not completely eliminate the beneficial arthropods. The Orius spp population was significantly decreased in all treated plots after 3 day of application insecticides in comparison to control. The arrangement pesticides according to high percent reduction were imidacloprid and insignificantly between acetamiprid and spinosad followed by cypermethrin and the lowest were chlorpyrifos, respectively after 3 day. Minimum level of reduction was achieved by spinosad and chlorpyrifos among all the insecticide after 7 days of spraying, follwed by cypermethrin, acetamiprid and Imidacloprid respectively. Degree of selectivity of chlorpyrifos, acetamiprid and spinosad were good selective, cypermethrin was selective and imidacloprid was medium selective.
C.Effect of the tested insecticides on the population density of Paederus alfierii on Horus plants in 2009 seasons.
the population larvae and adults of density Paederus alfierii on Horus plants were insignificantly varied from plants in all the treatments before application of insecticides in the year 2009. The tested compounds did not completely eliminate with the beneficial arthropods. The larvae and adults population were significantly decreased in all treated plots after 3 day of application insecticides in comparison to control. The arrangement pesticides according to high percent reduction were cypermethrin, chlorpyrifos, spinosad, acetamiprid and the lowest imidacloprid, respectively after 3 day. Minimum level of reduction was achieved by imidacloprid among all the insecticide after 17 days of spraying, followed by acetamiprid, spinosad, chlorpyrifos and cypermethrin respectively. The percent reduction of all the insecticides after 37 days of spraying was increased. Imidacloprid was again the lowest effective followed by acetamiprid, spinosad, chlorpyrifos and cypermethrin which reduced respectively. Degree of selectivity of imidacloprid, acetamiprid and spinosad were good selective, chlorpyrifos was selective and cypermethrin was medium selective.
Effect of the tested insecticides on the population density of Paederus alfierii on Dorado plants in 2009 season.
the population larvae and adults of density P. alfierii on Dorado plants were insignificantly varied from plants in all the treatments before application of insecticides in the year 2009. The tested compounds did not completely eliminate the beneficial arthropods. The larvae and adults population was significantly decreased in all treated plots after 3 day of application insecticides in comparison to control. The arrangement pesticides according to high percent reduction were cypermethrin and chlorpyrifos, acetamiprid, spinosad, and the lowest imidacloprid, respectively after 3 day respectively. Minimum level of reduction was achieved by imidacloprid among all the insecticide after 17days of spraying, followed by acetamiprid, spinosad, chlorpyrifos and cypermethrin respectively. The percent reduction of all the insecticides after 37, days of spraying were increased. Imidacloprid was again the lowest effective followed by acetamiprid, spinosad, chlorpyrifos and cypermethrin which reduced the P. alfierii population respectively. Degree of selectivity of imidacloprid, acetamiprid and spinosad were good selective, chlorpyrifos was selective and cypermethrin was medium selective.
Effect of the tested insecticides on the population density of Scymnus cyriacus on Horus plants in 2009 season.
The population larvae and adults of density S. cyriacus on Horus plants were insignificantly varied from plants in all the treatments before application of insecticides in the year 2009. The tested compounds did not completely eliminate with the beneficial arthropods. The larvae and adults population were significantly decreased in all treated plots after 3 day of application insecticides in comparison to control. The arrangement pesticides according to high percent reduction were cypermethrin, chlorpyrifos, spinosad, acetamiprid and the lowest imidacloprid, respectively after 3 day. Minimum level of reduction was achieved by imidacloprid among all the insecticide after 17 days of spraying, recorded with 5.7 percent reduction over control, followed by acetamiprid, spinosad, chlorpyrifos and cypermethrin respectively. The average number of Scymnus cyriacus in control and all treatments were decrease and the percent reduction of all the insecticides after 37 days of spraying was increased. The average number of Scymnus cyriacus in plots which treatment with midacloprid was equal with control and not reduction over control followed by acetamiprid, spinosad, chlorpyrifos and cypermethrin which reduced the Scymnus cyriacus population respectively. Degree of selectivity of imidacloprid, acetamiprid were good selective, spinosad, chlorpyrifos and cypermethrin were selective.
Effect of the tested insecticides on the population density of Scymnus cyriacus on Dorado plants in 2009 season.
The population larvae and adults of density Scymnus cyriacus on Dorado plants were insignificantly varied from plants in all the treatments before application of insecticides in the year 2009. The tested compounds did not completely eliminate the beneficial arthropods. The larvae and adults population was significantly decreased in all treated plots after 3 day of application insecticides in comparison to control. The arrangement pesticides according to high percent reduction were cypermethrin and chlorpyrifos, acetamiprid, spinosad, and the lowest imidacloprid, respectively after 3 day. Minimum level of reduction was achieved by imidacloprid among all the insecticide after 17 days of spraying followed by acetamiprid, spinosad, chlorpyrifos and cypermethrin recorded respectively. The percent reduction of all the insecticides after 37, days of spraying were increased. Imidacloprid was again the lowest effective followed by acetamiprid, spinosad, chlorpyrifos and cypermethrin which reduced the Scymnus cyriacus population respectively. Degree of selectivity, imidacloprid was good selective.while acetamiprid and spinosad were selective, chlorpyrifos and cypermethrin were medium selective.
4.2. Effects of intercropping of sorghum and cowpea on abundance and susceptibility to aphid population
This part of present study is an attempt to evaluate different systems of sorghum alternating with different rows of cowpea on the infesting of R. maidis and S. graminum and looking for the best patterns could reduce aphid infestation to the least level, hence saving crop and increasing crop yield.
4.2.1. Effect of intercropping sorghum with cowpea on the population density of R. maidis on Horus and Dorado plants in 2008 and 2009 seasons.
In Horus and Dorado plants, corn leaf aphid is a destructive pest of sorghum and threatens crop yield, therefore this pest was taken into consideration in field. experiments were conducted. Sorghum infestation by R. maidis was markedly affected by cultural system of sorghum and cowpea. Infestation degree on sorghum was considerably high on sorghum plants as a monoculture than when maize intercropped with cowpea in different patterns.
Infestation rate by corn leaf aphid evidently reduced by intercropping sorghum / cowpea in different patterns compared with sorghum monoculture. the least infestation levels of maize by R. maidis were achieved in heterogeneous plots where cowpea was alternated with maize at 2:2 or 2: 1 rows sorghum : cowpea; the highest percentage of infested plants was observed in plots with 4:2 rows sorghum : cowpea.
4.2. Effect of intercropping sorghum with cowpea on the population density of S. cretica on Horus and Dorado plant in 2008 and 2009 seasons.
This part of present study is an attempt to evaluate different systems of sorghum alternating with different rows of cowpea on the abundance and occurrence of S. cretica and response of the two crops to S. cretica infestation under such polyculture systems. Furthermore, looking for the best patterns could reduce S. cretica infestation to the least level, hence saving crop and increasing crop yield.
In Horus plants
Infestation rate by S. cretica evidently reduced by intercropping sorghum / cowpea in different patterns compared with sorghum monoculture. the least infestation levels of sorghum by S. cretica were achieved in heterogeneous plots where cowpea was alternated with sorghum at 2:2 sorghum: cowpea
In Dorado plants
The highest percentage of infestation was observed in the case of 4:2 rows sorghum : cowpea and the lowest degree of infested plants occurred in plots with 2:2 rows sorghum / cowpea compared with for pure sorghum. Intercropping patterns of sorghum considerably affected the infestation rate of sorghum by S. cretica. These results reveal that S. cretica infestation of sorghum cropped with cowpea markedly reduced by cropping pattern employed. This conclusion is clearly noticed through reduction percentage of S. cretica of sorghum.
4.1.2. Effect of nitrogen fertilization on the pests density in sorghum plants:-
4. Effect of two level fertilization on the population density of R. maidis on Dorado plants in 2008 and 2009 season.
In two seasons, early and late season the population of aphids increased significantly with the decrease in the nitrogen fertilization,
Significant differences were found between the numbers of aphids on plants received different rates of N-fertilization, since, the numbers of aphid regardless of planting dates. The numbers were correlated with the rates of N-fertilization received.
4. Effect of two level fertilization on the population density of R. maidis on Hroras plants in 2008 and 2009 season.
In 2008 and 2009 seasons, the population of aphids on the early planting date were decreased significantly with the increased in the nitrogen fertilization.
In the late date of 2008 season, the population of aphids were increased significantly with the increased in the nitrogen fertilization.
4. Effect of two level fertilization on the population density of Schizaphis graminum on Dorado plants in 2008 and 2009 season.
in two seasons, early and late season the aphids population increased significantly with the decrease in the nitrogen fertilization, Significant differences were found between the numbers of aphids on plants received different rates of N-fertilization, since, the numbers of aphid regardless of planting dates. The numbers were correlated with the rates of N-fertilization received.
4. Effect of two level fertilization on the population density of S. graminum on Hroras plants in 2008 and 2009 season.
in 2008 and 2009 season, the population of aphids on the early planting date were decreased significantly with the increased in the nitrogen fertilization.
In 2008 season, the population of aphids on the plants of latest planting date were increased significantly with the increased in the nitrogen fertilization.
4. Effect of two level fertilization on the population density of S. cretica on Horus and Dorado plants in 2008 and 2009 season:-
On Horus plants
The differences between the tested sorghum cultivars when supplied with two levels of nitrogen fertilizer (80 and 120 units/feddan, respectively), with respect to either the percent reduction of leaf-feeding or dead-heart and the infestation as a whole were statistically insignificant. This means that an increase in the level of nitrogen fertilizer from 80 kg/feddan to 120 kg/feddan caused a significant decreased in the borer infestation, respective of sorghum cultivar in early sowing date, also the population of S. cretica on the late planting date were increased significantly with the increased in the nitrogen fertilization from 80 kg/feddan to 120 kg/feddan.
On Dorado plants
the differences between the tested sorghum cultivars when supplied with two levels of nitrogen fertilizer, with respect to either the mean percentages of leaf-feeding or of dead-heart and the infestation as a whole, were statistically insignificant. This means that an increase in the level of nitrogen fertilizer from 80 kg/feddan to 120 kg/feddan caused a significant decreased in the borer infestation, irrespective of sorghum cultivar in the early and late sowing date in 2008 and 2009 season.
Relative susceptibility of two Sorghum tested varieties to infestation with the corn leaf aphid, R. maidis and S. graminum in 2008 and 2009 seasons:-
Data revealed differences in average number of aphids/plant among sorghum varieties (Horus as long plants and Dorado short plants). These data reveled that in 2008 season, numbers of aphid on all varieties were increased gradually from the beginning of the season to reach its peak by the end of August. Then it started to decrease gradually again by the beginning of September. Dorado plants were the higher susceptibility than Horus and significant differences between them.
Relative susceptibility of two sorghum tested varieties to infestation with the S. cretica infestation in 2008 and 2009 seasons:-
The infestation percentages of S. cretica against sorghum varieties were generally increased gradually with the plant age. Percentage of infestation was reached its peak by the middle of June and early of September in both tested seasons in all tested varieties. According to the overall average in 2008 and 2009 seasons Horus plant were the most tolerant to be infested by S. cretica followed by Dorado plants variety with insignificant difference between them.
Effect of sowing dates on the sorghum infestation by R. maidis and S. graminum infestation:
In both Horus and Dorado plants the late date on June 2, received a higher population than those of the early sowing date, on May 22, and there are insignificant difference between numbers of aphid on plants at two sown. The higher numbers of aphids was on the late sowing Dorado plants, and the lowest on the early Horus plant. Dorado plants were received a higher population of R. maidis and S. graminum than Horus plants at two sowing dates. The population of R. maidis was higher than population of S. graminum at two sowing dates and in both Horus and Dorado plants.
Effect of sowing dates on the sorghum infestation by Sesamia cretica infestation
The results of analysis of variance differences dealing with leaf-feeding, dead heart and the infestation as a whole showed that there are significant differences between cultivars susceptibility to infestation by S.cretica in May (18) as first sowing dates and June (2) and second sowing dates. However, as regards to the leaf-feeding infestation significant differences were observed in the mean infestation percentages. from the obtained findings, it could therefore be logical to state that Horus and Dorado plants were the least susceptible cultivars by S. cretica in May (18) as first sowing dates while Horus and Dorado plants demonstrated the most susceptible in June (2) as second sowing dates.
Relation between predators and culture practices in sorghum plants
4.2. Effects of intercropping of sorghum and cowpea on abundance and susceptibility to some predators population
This part of present study is an attempt to evaluate different systems of sorghum alternating with different rows of cowpea on the abundance and occurrence of the some predator’s population and response of the two crops to predators population under such polyculture systems. Furthermore, looking for the best patterns could increased predators population to the high level, hence saving crop and increasing crop yield.
predator’s population on sorghum plants were markedly affected by cultural system of sorghum and cowpea. Predator’s population degree on sorghum was considerably high on sorghum plants when a intercropped with cowpea in different patterns than monoculture.
predator’s population increasing by intercropping sorghum / cowpea in different patterns compared with sorghum monoculture. As shown in Table (), the least predator’s population levels of sorghum by R. maidis were achieved in heterogeneous plots where cowpea was alternated with sorghum at 4:2 or 2: 1 rows sorghum : cowpea; the highest percentage of predator’s population was observed in plots with 2:2 rows sorghum : cowpea.
B. Effect of doses fertilization in tested sorghum varieties on certain predators.
the population of predators were increased with the increased in the nitrogen fertilization in tested sorghum varieties.
C. Effect of sowing date in tested sorghum varieties on certain predators
The predators activity started in half of June and continued until the second half of Sept. It was generally noticed that Scymnus cyriacus appeared before Orius spp. and later before Coccinella undecimpunctata and Paederus alfierii. Predators in late sowing date were higher than early sowing date. It is generally assumed that they correlated with aphid activity and presence.
Effect of tested sorghum varieties on certain predators.
It was very clear that short varieties e.g. Dorado with wide-leaves attracted more predators than long varieties. This valid for C. indecimpunctata, and Orius spp. and Paederus alfierii for 2009 season.
These short varieties may offer very good microhabitat for predators with good availability of preys (Aphids). Predators on Dorado as short varieties were higher than on Horus as long varieties.