الفهرس 
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Abstract
The present work is an attempt to study some biological and ecological aspects of the two main cotton insect pests, in addition to estimate the thermal requirements needed for development and predicting seasonal activity and annual field generations for both pests. All experiments were carried out in the laboratory of Ecological Studies, Department of Plant Protection, Faculty of Agriculture, Ain Shams University and cotton fields at Qalyubia, Sharkia and Monufia Governorates.
A. Biological studies:
1. Spodoptera littoralis
1.1. Egg stage:
The incubation period
The mean of incubation periods were 10.00, 6.00, 4.00, 3.64, 2.64 and 2.00 days at 15, 20, 23.5, 25, 30, and 35oC, respectively. The longest mean of incubation period was 10 days at 15oC, while the shortest one was 2 days at 35oC.
Percentage of hatchability
The highest percentage of hatchability (99%) was obtained at 23.5oC.; the lowest (5.3%) was obtained at 15oC. The percentages of hatchability were 82, 98.4, 94.5 and 46.4% at 20, 25, 30 and 35oC, respectively.
Threshold of development
The threshold of development was 11oC.
Thermal requirements
The average of thermal units required for development was 48.85 degree-days.
1.2. Larval stage:
Duration
The mean of S. littoralis larval durations at six constant temperatures 15, 20, 23.5, 25, 30 and 35ºC were 63.0, 28.0, 24.2, 22.0, 15.7 and 13.5 days, respectively.
Threshold of development
The threshold of development was 9oC.
Thermal requirements
The average of thermal units required for larval development was 351.73 degree-days.
1.3. Pupal stage:
Duration
The pupal periods decreased as temperatures increased. The average durations were 29.92, 19.56, 18.12, 10.46, 6.00 and 5.58 days at 15, 20, 23.5, 25, 30 and 35ºC, respectively.
Threshold of development
The threshold of development was 13.12oC.
Thermal requirements
The average of thermal units required for development was 121.09 degree-days.
1.4. Adult stage
1.4.1. Adult longevity
There was a tendency for adult life to be reduced at high temperatures.
1.4.2. Male duration
The means of male longevity was decreased as temperature increased. Means of longevity was 15.84, 15.08, 10.56, 5.48 and 3.00 days, at 20, 23.5, 25, 30 and 35oC, respectively.
Threshold of development
The threshold of development was 18.77oC.
Thermal requirements
The average of thermal units required for development was 53.36 degree-days.
1.4.3. Female duration
Pre-oviposition period
The mean of pre-oviposition periods for S. littoralis at different temperatures were 4.56, 2.00, 2.00 and 1.40 days at 20, 23.5, 25 and 30ºC., respectively. Females emerged from pupae reared at 15oC were few and didn’t complete its life cycle, on the other hand, females emerged at 35oC were malformed and couldn’t mate with healthy males.
Oviposition period
Oviposition periods of S. littoralis femles were 9.00, 11.00, 9.28 and 4.40 days at 20, 23.5, 25 and 30ºC., respectively.
Post-oviposition period
Post-oviposition periods of S. littoralis females averaged 5.00, 2.68, 1.68 and 1.00 days at 20, 23.5, 25 and 30ºC., respectively.
Generally Females lived longer than males at the five tested temperatures. Means of S. littoralis females longevity were 18.56, 15.68, 12.96, 6.80 and 4.20 days at 20, 23.5, 25, 30 and 35oC., respectively.
Fecundity
The mean of eggs laid/ female were 2790, 4003, 4392 and 2898 eggs at 20, 23.5, 25 and 30oC., respectively.
Sex ratio
Sex ratio at the four constant temperature 20, 23.5, 25 and 30oC were 1:1.06, 1:1.47,1: 1.38 and 1:0.85 (M:F).
1.5. Generation duration
The shortest duration of generation was achieved at 30oC being 25.74 day; while the lowest one occurred at 20oC being 58.12 days. The threshold of development was 13.19ºC. The average of thermal units required for completing a generation was 444.16 degree-days.
2. Pectinophora gossypiella
Laboratory experiments revealed the following:
2.1. Egg stage:
Any increase in temperature was found to shorten the duration of the egg stage. The incubation periods were 10.86, 10.29, 6.00 and 4.00 days at 18, 20, 25, and 30oC.
The percentages of eggs hatchability were 78, 89, 98 and 84% under 18, 20, 25 and 30oC, respectively.
The estimated threshold of development for egg stage was 12.1oC and the average of thermal units required for egg development was 73.59 degree-days.
2.2. Larval stage:
The mean of P. gossypiella larval durations at the four tested constant temperatures 18, 20, 25 and 30ºC were 47.61, 36.61, 20.70 and 16.60 days, respectively.
The estimated threshold of development for larval was 11.6oC, while the average of thermal units required for development of larval stage was 298.76 degree-days.
2.3. Pupal stage:
The pupal periods decreased as temperature increased. The average durations were 20.13, 19.20, 9.85 and 7.40 days at 18, 20, 25 and 30ºC, respectively with an average of 14.1 days.
The estimated developmental threshold for pupal stage was 12.1oC and the average of thermal units required for development of the pupal stage was 124.98 degree-days.
2.4. Adult stage:
The obtained results revealed that there was a tendency for adult male and female lives to be reduced at high temperatures.
2.4.1. Male duration and thermal requirements:
The mean of male longevity decreased as temperature increased. Mean longevity was 33.59, 27.72, 23.82 and 13.75 days, at 18, 20, 25 and 30°C, respectively. The estimated threshold of development was 9.8oC and the average of thermal units required for development was 299.5 degree-days.
2.4.2. Female duration and thermal requirements:
Pre-oviposition period
The pre-oviposition periods for P. gossypiella females at different temperatures were 7.79, 6.75, 4.52 and 3.48 days at 18, 20, 25 and 30ºC., respectively.
Oviposition period
The means of oviposition periods at different temperatures were 12.20, 15.35, 19.82 and 8.00 days at 18, 20, 25 and 30ºC., respectively.
Post-oviposition period
The means of post-oviposition periods at different temperatures were 13.69, 8.90, 4.30 and 3.16 days at 18, 20, 25 and 30ºC., respectively.
Generally females lived longer than males at the four tested temperatures. The mean of female longevity decreased as temperature increased. Means of P. gossypiella females longevity were 33.68, 31.00, 28.64, 14.64 days at 18, 20, 25 and 30oC., respectively. The threshold of development was 9.8 ºC. The mean of thermal units required for adult female was 338.96 degree-days.
Fecundity
The highest mean number of eggs laid/ female (232.17 eggs) was obtained at 25°C, while at 18oC, considerable reduction in mean number of eggs, (32.39 female) was occurred.
Sex ratio
Recorded sex ratio at the four constant temperature 18, 20, 25 and 30oC were 1: 1.44, 1: 1.04,1: 1.27 and 1: 1.12 (M:F). It’s clear that the highest ratio of females was occurred at the lowest temperature of rearing.
2.5. Generation duration
The shortest duration of generation was achieved at 30oC being 31.48 day; while the lowest one occurred at 18oC being 86.39 days. The threshold of development was 11.7ºC and the average of thermal units required for completing one generation was 567.81 degree-days.
B. Ecological studies:
The ecological studies were carried out in the cotton fields located at three districts as follows; Shalaqan, (Qalyubia Governorate) during 2017 and 2018, Quwaysina (Monufia Governorate) during 2018 and 2019, and El-Saadien (Sharkia Governorate) during 2018 and 2019.
Water traps provided with sex pheromone capsules were used for monitoring the population activity of CLW, while delta pheromone traps were used for monitoring CPW. Weekly numbers of male moths of both S. littoralis and P. gossypiella male moths caught in water pheromone traps or in delta pheromone traps were used for determining the seasonal activity and numbers of annual field generations in addition to occurrence dates of generation peaks, as necessary information, required for planning management programs of these insect pests in cotton fields.
Three methods used to achieve this purpose were:
a) Normal distribution curve (fluctuation curve)
b) Statistical method (scale Gauss or regression lines)
c) Accumulated thermal requirements (DDs)
A) Spodoptera littoralis:
The obtained results revealed that cotton leafworm S. littoralis had seven generations annually based on careful examination of the fluctuation curve and regression lines during first season (2017) at Qalyubia Governorate, while during the second season (2018), eight generations annually were recorded as compared to seven generations per year during the two seasons when accumulated heat units method was used. There is a coincidence between dates of peaks occurrence of the recorded generation with deviation of ± 2-4 days.
At Sharkia Governorate, eight generations of S. littoralis were detected annually by applying normal distribution curve and accumulated thermal units during the two seasons (2018 and 2019) as compared to only seven generations per year when regressions lines was used to estimate the numbers of annual field generations. Peaks of generations nearly occurred in the same dates with maximum ±2 days deviation.
At Monufia Governorate, eight generations of S. littoralis were detected annually during the two tested years (2018 and 2019) when normal distribution curve and accumulated heat units were used, while regression lines method resulted eight generations annually during 2018 and only seven generations were detected during the second season, 2019, occurrence peaks of generations took place nearly in the same dates with maximum deviation of ±2 days.
B) Pectinophora gossypiella:
Laboratory study demonstrated that the average of accumulated thermal units required for completing one generation of P. gossypiella was 567.81 DDs.
At Sharkia Governorate, obtained results showed that P. gossypiella had five observed field generations during the first season 2018, based on fluctuation curve, also five field generations were predicted when the accumulated heat units reached 556.14, 568.12, 572.00, 561.30 and 559.70 DDs. Peaks of generations occurred nearly in the same dates.
Data obtained during 2019 revealed the presence of six field generations when the two methods (fluctuation curve and thermal units) were used, furthermore, peaks of generations occurred in the same dates.
When regression lines (Scale Gauss) were used to estimate annual field generations of P. gossypiella; four and five generations were detected during 2018 and 2019 respectively.
At Monufia Governorate, different methods used for estimating annual field generations of P. gossypiella, demonstrated that the pest had five generations annually. Data also revealed the presence of high coincidence between dates of generations peaks, third, fourth and fifth generations are the most economic important, start emerging of adult moths early in the season is mainly depend on the prevailed temperature, Furthermore, the coincidence between adult moths emergence early in the season and the appearance of infestation receptors (green buds, flowers and green bolls) are the main factor for infestation development in cotton fields.