الفهرس 
CONTENTES
Effect of different host plants on S. littoralisOnly 14 pages are availabe for public view
 |  | from | 32 |  |  |
| | | from | 32 | | |
Abstract
- Biological studies: - Effect of temperature on immature and mature stages of S. littoralis:
The first part of this study was carried out to study the effect of three constant temperatures 20, 25 and 30°C on the differed stages of S. littoralis.
1- In egg stage, the highest percent of hatchability was 80.84% which was recorded at 30°C whereas the lowest one was 63.13% at 20°C.
2- The thermal units required for egg development at three tested temperatures 20, 25 and 30°C were 40.21, 52.01 and 47.07 day- degrees, respectively, with an average of 46.42+5.93 days-degrees, whereas the t0 was 10.47°C.
3- In larval stage, the highest percentage of larval survival was 92.86% which was recorded at 30°C whereas at 20ºC and 25°C were 86.66% and 84.75%, respectively.
4- The total quantity of thermal energy required for the larvae to complete their development were 157.31, 183.89 and 168.50 day-degrees at 20º, 25 ºand 30°C, respectively.
5- In pupal stage, the longest period was 4.88+0.07 days which was recorded at 20°C while the shortest was1.36+0.09 days that was observed at 30°C.
6- The thermal units required for pupa to complete its development at studied temperature were 57.21, 38.69 and 26.48, respectively with an average of 37.12 day-degree.
Effect of temperature on the adult stage:
a - Ovipositon periods :
This study showed the following results:
- The pre-oviposition period were 3.2±0.42 , 2.3±0.48 and 1.3±0.48 days at 20˚,25˚,30˚ C, respectively.
- The ovipostion period reached 4.6±0.52 , 3.5±0.53 , and 3.1±0.32 day at 20˚,25˚ and 30˚C, respectively.
- The post-ovipostion period were 2.5±0.53 , 2.9±0.57 and 1.6±0.5 days at 20˚, 25˚ and 30˚C, respectively.
The previous results concluded that :
Temperature had a significant effect on the pre-oviposition periods.
The longest pre-oviposition period was recorded at 20°C.
Ovipositon period decreased with the raising temperature.
b- Fecundity:
The highest fecundity was of S. littoralis was recorded at 25°C whereas the lowest fecundity was appeared at 20°C.
c- Certain life table parameters:
The life table parameters were as following:
The survival patterns at 20°C declined to 50% after 9 days whereas at 25°C it declined to 50% of population after 7 days. At 30°C, population of adults declined to 50% after 6 days.
The net reproduction rates (R0) were 54.78, 235.16 and 189.5 at the three constant temperatures of 20˚, 25˚ and 30°C, respectively. Mean generation time (GT) was 47.78, 30, 21 and 20.9 days, whereas the population doubling time (GT) was 8.281, 3.85 and 2.772 days respectively.
The values of intrinsic rate of increasing (rm) of cotton leafworm at 20˚, 25˚ and 30°C were 0.0837, 0.180 and 0.250 whereas the finite rare of increasing were 1.087, 1.197 and 1.284, respectively.
Data showed also that under Assiut conditions, the pest could develop about 16 generations per year.
5.1.2- Effect of different host plants on the biology of S. littoralis:
In this part of the study, four leaf plants were used in feeding of larvae of S. littoralis namely tomato, egg plant, castor and cotton and the results appeared that:
1- The leaves of cotton larval diet is the most effective in shorting the pupal stage.
2- The heaviest mean of pupa weight 0.393 mg was obtained from those fed on egg plant leaves, whereas, the pupa fed on cotton leaves produced the lightest mean weight (0.198 mg).
3- The effect of larval found on the oviposition periods appeared that the longest mean duration of the oviposition period was obtained with females which their larvae reared on egg plant leaves and the shortest with females which reared their larvae on castor and cotton leaves.
a -Adult longevity
The longevity period of S. littoralis males was the longest with an average of 7+0.67 days when their larvae reared on egg plant leaves and the shortest was 5.7+0.48 days that produced on male when reared their larvae on tomatoes leaves.
b - Fecundity of mated females:
Female moth originated from larval fed on castor and cotton leaves laid the highest mean number of eggs.
Castor and cotton leave as larval food ranks the first place among the tested host plants concerning its effect on increasing the fecundity of the resulting females.
5.2- Toxicity of biopesticides, essential oil of black pepper, and indoxacarb on S. littoralis larvae:
The second part of this study was carried out to evaluate the efficacy of four biopesticide formulations, and the essential oil, Black pepper extract (Piper nigrum) in comparison with conventional insecticides (Inoxacarb) against S. littoralis. The experiments were conducted on laboratory strains in Assiut Governorate.
Results achieved throughout this part of this study could be summarized as follows:
1- The most toxic tested compound against second instar larvae after 24 h was Emamectin benzoate (5% SG), and the LC50 value was 0.02 µg/ml, whereas the LC50 of the lowest toxic compound Spinetoram (12% SC) was 9.36 µg/ml. The moderate toxic compounds were Azadirachtin (0.03% EC), Black pepper extract, B. bassiana (1x108 condial/ml3), and indoxacarb (15% SC) and the values of LC50 were 0.39, 0.73, 1.02 and 1.47 µg/ml, respectively.
2- After 48 h, the LC50 values dramatically decreased and the LC50 value of Emamectin benzoate (5% SC) and indoxacarb (15% SC) were 0.05 and 0.25 µg/ml, respectively.
3- After 72 h the LC50 values continued to decrease to be 0.001 and 0.04 µg/ml of Emamectin benzoate and Indoxacarb, respectively.
4- LC50 values of B. bassiana (1x108 condial/ml3) were decreased significantly to be 0.05 µg/ml after 72 h.
5- The toxicity of the tested compounds against the second instar larvae, was increased after 48 and 72 h. Emamectin benzoate increased in toxicity from 4.00-fold after 48 h to 20.00-fold after 72 h, however, Beauveria bassiana increased in toxicity from 2.13-fold after 48 h to 20.4-fold after 72 h.
6- Against second and fourth instar after 24 h the toxicity index of Emamectin benzoate was 100%, whereas for Azadirachin, Black pepper extract, B. bassiana, Indoxacarb, and Spinetoram after 24 h were 5.3%, 2.7%, 1.96%, 1.36 and 0.21%, respectively on second instar, and 21.13%, 15.15%, 8.52%, 5.32% and 1.00%, respectively, on fourth instar.
7- According to tolerance ratio (TR) values, between various larval instars in the laboratory stains, the hight TR was net with B. bassiana after 72 h (TR= 11.00) whereas the TR of Emamectin benzoate after 24 h was (TR= 7.5).
8- Generally, the second instar larvae were more sensitive to the six tested compounds than to the fourth instar larvae of S. littoralis. It might conclude that Emamectin benzoate is considered the most potent biopesticide among all tested compounds.