M. A. Al-Allan
General Commission for Scientific Agricultural Research, Administration of Plant Protection
Damascus University, Faculty of Agriculture
2009

abstract

this study has been carried out in order to determine some biological and ecological aspects which are important to control corn stem borer. The Morphological studies showed significant differences in body length and wing width between male and female (p ≥ 0.01). Eggs dimeter and thickness were 745± 5.12 µ.m. and 423.2± 1.25 µ.m. respectively, with disciform shape and special structures. Larvae has 7-9 instars according to rearing temperature. Instars are different significantly (p ≥ 0.01) in length, width (except 6^th vs 7^th), capsule length (except 7^th vs 9^th) and capsule width. Also there were significant differences (p ≥ 0.01) in  pupal length and width between male and female. The biological and ecological studies showed that light traps with halogen lamp was more attractive to corn stem borer S. cretica than neon lamp light trap (p ≥ 0.01). This study showed that there were two generations and starting of third one per year. Noctuid flight activity showed significant positive correlations with mean temperature, evaporation ratio and sun light, this correlation was  negative with relative humidity, regression lines and equations has been been established for these correlations. High positive correlation was found between numbers of male and numbers of female traped in light traps. Laboratory studies showed that adults longevities (male and female) were significantly different under different rearing temperatures, and there were significant differences between male and female longevities under all rearing temperature used except 25 C°. development rates were significantly different under different rearing temperature for both male and female, with exceptional 30 C°,35 C°. the development threshold was 15.09 C° and heat budgets was 704.65 degree-day. Female layied 132.87±9.53 eggs during 4.29±0.14 days under 25 C°. the egg incubation periods were negatively correlated with temperatures. it had been found that the favorite temperature, the development threshold and the heat budget for embryo development were 35 C°, 12.27 C°, and 148.65 degree-Day respectively. The rate of egg hatching was negatively correlated (r = -0.95) with the periods of cold temperature exposure of the eggs. Also it was found that there were positive correlation between exposure times and incubation periods (r = 0.99). Field studies showed that there were two peaks of egg densities in Durra season, and there were significant correlation between egg densities and sun light in 2005 season only. larval densities  had significant negative correlation with mean temperature, sun light and evaporation factor, this correlation was positive with mean humidity, and absent with wind speed. Laboratory studies showed seven  larval instars at 25 C°. number of instars increase to nine at 15 and 20 C°. the larval development rates were different significantly at different rearing temperatures (p ≥ 0.01). The larval development threshold and the larval heat budget were 13.89 C°. and 413.38 degree-Day respectively. Larval pupation started in the beginning of February and it had been found two peaks of pupal densities in the field. Laboratory studies showed significant (p ≥ 0.01) pupal development rates under different rearing temperatures with exception of 30 C° vs 35 C°. pupal development threshold and pupal heat budget were 7.69 C°. and 287.8 degree-Day respectively. The control studies showed that the cultivar Izraa-7 was more resistance for corn stem borer than Izraa-5 in seedling stage only. No significant differences in infestation by corn stem borer between the two cultivation dates 8 June and 15 July. Desis-D treatment showed a significant effects comparing with the control while there were no significant differences in effects between Summer oil and Desis-D treatments.