الفهرس 
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Abstract
All experiments of the present study were carried out at the Experimental Research Station, at Qaha, Qalyoubia governorate during three successive seasons (2020,2021and 2022) and laboratories of cotton bollworms(CBW) division affiliated to Plant Protection Research Institute (PPRI), Agricultural Research Center (ARC), Dokki, Giza.
The results obtained could be summarized as follows:
1. Biological features of O.hyalinipennis:
1.1. Egg stage:
The required time for embryonic development (incubation period) decreased as the temperature increased the mean incubation periods were 6.66, 5.66 and 4.33 days at 25±1 ˚C, 30±1˚C and 35±1˚C. the threshold of eggs development was 7˚C. the average of thermal units needed for development of egg stage was 123.8 DD’s. Also the obtained results revealed that temperature has significant effect on eggs hatchability, this percentage was estimated at three constant temperatures the highest percentage was recorded at 25±1˚C where it was 95% while it was 83% at 35±1˚C.
1.2. Nymphal stage:
Data obtained revealed that temperature has a highly significant effect on the development of nymphal stage, the longest nymphal duration (25.2 days) was recorded at 25±1˚C while the shortest duration (13.88 days) was recorded at 35±1˚C, threshold of development for nymphal stage was estimated as 12.51˚C and the thermal units required for completion nymphal stage was determined as 285.36 DD’s, furthermore the highest percent of nymphs succeeded grown up into adults (95%) was recorded at 25±1˚C. Although, the shortest period of nymphal duration was recorded at 35±1˚C, the highest nymphal mortality (22%) and the lowest percent of nymphs turned into adults (78%) occurred at 35±1˚C.
1.3. Adult stage:
All phases of female (pre, Ovi- and post ovipositional periods) and male longevity were found highly affected by increasing temperature, these periods were 48.0, 23.33 and 13.51 days for female and 55.75, 28.70 and 17.26 days for male at 25±1˚C, 30±1˚C and 35±1˚C, respectively. Threshold of development was estimated as 13.85 and the thermal required for adult stage was 421.36 DD’s. the adult males usually lived more than adult females at all tested temperatures.
1.4. Fecundity of females and eggs fertility:
Data revealed that female fecundity severely decreased with the increasing of temperature, where the average number of eggs/ female were 227.7, 123.8 and 83.0 at 25±1˚C.30±1˚C and 35±1˚C, respectively. The highest fertility of eggs (95%) was recorded at 25±1˚C and the lowest (83%) was at 35±1˚C.
1.5. Sex Ratio:
Obtained results demonstrated that sex ratio of O. hyalinipennis was highly affected by temperature, whereas the sex ratio nearly equal (1♂: 1.1♀) at 25±1˚C and become 1.4 for male against 1 for female at 30±1˚C, then 1.94 for males against 1 for female, at 35±1˚C. It is clear that percent of males increased with the increasing of temperature.
1.6. Life table parameters:
The life table parameters of O. hyalinipennis specially net reproductive rate (Ro), Finite rate of increase (λ) and population doubling time (Dt) values revealed that 25±1˚C seems to be the most favorable temperature for O. hyalinipennis development, while the shortest generation time (Gt) was recorded at 35±1˚C.
2. Ecological Study:
Fluctuation of the population density of Oxycarenus hyalinipennis in cotton field were carried out for estimating the occurrence dates and numbers of field generations in addition to survey the host plants surrounding cotton fields for detection the presence of the considered pest and determination source of infestation to cotton plants.
2.1. Seasonal fluctuations:
Results revealed that the first appearance of O.hyalinipennis in cotton fields was occurred in the second half of June with few numbers and gradually increased, forming first small peak during July, then decreased during August and suddenly increased during September forming the highest peak, coincide with the increasing of opening mature bolls which make the way easy to reach both nymphs and adults to the cotton seeds, (the main food of the bug) the two peaks represent two field generations on cotton plants during both two seasons (2020 and 2021).
2.2. Estimated field generations:
When the weekly numbers of O. hyalinipennis individuals sampled by using in site count /100 cotton plants worked out according to the method suggested by Audemard &Miliare (1975) and Iacob (1977) enhanced the presence of two regression lines which represent two distant field generation, the first occurred during July and the second during September, with high population density, caused severely damage on cotton yield and quality these results confirmed that the oil of cotton seeds is the main limiting factor of the population increasing.
3. Effect of infestation levels on Oil % and germination of seeds:
3.1. Effect of nymphal stage feeding:
Results revealed highly significant effect of O. hyalinipennis nymphs infestation levels on both of the oil content in cotton seeds and seeds germination %. The significant reduction in oil% occurred at level of 20 nymphs/ 20 seeds reached its maximum at level of 100 nymphs/ 20 seeds as compared with control.
Regarding germination % of cotton seeds data revealed that, all levels of infestation caused significant decrease in germination % in cotton seeds, reaching zero% at level of 50 nymphs/20 seeds compared with the normal germination % in control (74.6%).
3.2. Effect of adult stage feeding:
The same results of the effect of infestation levels of O. hyalinipennis adults were detected on the oil% in cotton seeds and germination %, results revealed that the first three levels of adult infestation 5, 10 and 15 adults/20 cotton seeds have no significant effect on oil% in cotton seeds and from the beginning of 20 adults/ 20seeds caused significant reduction in oil% in seeds as compared to control. All levels of adults infestation caused highly significant reduce in seeds germination, reached zero % germination at level of 50 adults /20 seeds as compared to normal germination in control.
Conclusion
Finally, it could be concluded that O. hyalinipennis (costa) is a serious pest of cotton plants late in the season. Results revealed that this pest has two field generations on cotton plants, the first one with small size, occurred during July, while the second occurred during September, with high population density. The injurious of this generation is due to the coincide between rabidly increased in the population density of the second generation and opening of majority cotton bolls, resulting highly significant reduction in cotton yield, oil content of seeds, germination percentage, in addition to the contamination occurred in cotton fibers due to crushing different stages of O. hyalinipennis during processing of cotton, consequently, reducing cotton fibers quality.
Also the present study demonstrated that O. hyalinipennis nymphs and adults feed on many alternative host plants which present the main source of infestation to cotton plants in addition to nymphs and adults present in the waste of cotton bolls in stores and scattered open bolls in the fields. These results are very useful in planning management program of cotton pests.