Some aspects of the Biology of the Third Generation of Earias insulana Boisd. (Lep.: Noctuidae) Reared on Three Host Plants

Abstract

The spiny bollworm Earias insulana Boisd. (Lepidoptera: Noctuidae) is considered one of the major threats of okra and cotton in Sudan. Hambuk fruits, okra unripe seeds and milky grains of maize were proves as larval foods to investigate their effect on the development of the insect. The insects were reared on the different foods for three successive generations. Insects were also reared on Hambuk fruits and milky grains of maize for two successive generations and then the larval food was altered in the third generation to the other food. The food provided influences the larval and the pupal period and has a noticeable effect on the mortality percentage of the insects. Also it was observed that the type of food affected the fertility of mated female. The result showed that the mean larval duration on Hambuk fruits, unripe seeds of okra and milky grains of maize in the 1st generation were 8.49 =617; 0.81, 9.08 =617; 0.83 and 11.75 =617; 0.96 days respectively at room temperature 33.3°C and 34% R.H. and the mean larval mortality were 48, 47.3 and 93.5 respectively. In the 2nd generation the mean larval duration was 9.11 =617; 0.56, 9.04 =617; 0.42 and 11.25 =617; 0.75 days when the larvae were reared on Hambuk fruits, unripe seeds of okra and milky grains of maize, respectively at room temperature 35°C and 40% R.H. and the mean larval mortality percentage were 31.1, 27.4 and 88.8, respectively. In the 3rd generation the larval duration was 8.23 =617; 0.61, 8.41 =617; 0.79 and 10.78 =617; 0.88 days on the three foods, respectively. The mean larval duration for individuals which their food was altered to Hambuk fruits in the third generation was 8.69 =617; 0.91 days and for those which their food was altered to milky grains of maize in the 3rd generation was 11.71 =617; 0.85 days at room temperature 32.2°C and 42% R.H. and the mean larval mortality percentage was 36.6, 29.8, 78.6, 55.00 and 88.6 respectively. The mean pupal duration on Hambuk fruits, unripe seeds of okra and milky grain of maize in the first generation was 7.05 =617; 0.65, 7.98 =617; 0.39 and 9.00 =617; 0.00 in the 2nd generation was 7.76 =617; 0.29, 6.95 =617; 0.27 and 8.86 =617; 0.69, respectively. The mean pupal duration in the 3rd generation were 7.23 =617; 0.53, 7.18 =617; 0.43, 8.67 =617; 0.71, 6.75 =617; 0.65 and 8.90 =617; 0.88 days respectively. Whereas the mortality percentage of the pupa in the 1st generation were 23.5, 24.2 and 50.0 respectively. In the 2nd generation were 16.7, 28.5 and 41.7 respectively and in the 3rd generation were 14.1, 11.0, 50.0, 22.2 and 41.2 respectively. In the 1st generation the average time from egg to emergence of male was 19.1 =617; 0.6, 20.1 =617; 0.6 and 23 =617; 0.0 days respectively. In the 2nd generation the duration was 19.2 =617; 0.7, 19.3 =617; 0.9, 22.8 =617; 0.5, 18.9 =617; 0.7 and 23.0 =617; 0.8 days respectively. The average time from egg to the emergence of the female in the 1st generation was 19.3 =617; 0.7, 20.4 =617; 0.7 and 23.0 =617; 0.0. In the 2nd generation was 19.5 =617; 0.8, 19.2 =617; 0.7 and 23.2 =617; 0.8 and in the 3rd generation was 19.3 =617; 0.9, 19.4 =617; 0.9, 23.2 =617; 0.8, 19.2 =617; 0.6 and 23.3 =617; 0.6 days respectively. It was observed that there were an increase in the length of the different developmental stages and also in the mortality percentage when the provided food was the milky grains of maize compared to those fed on Hambuk fruits or on the unripe seeds of okra during the three rearing generations.