G. Nahar
Institute of Food and Radiation Biology, Atomic Energy Research Establishment (AERE), G.P.O Box 3787, Dhaka, Bangladesh.
A. J. Howlader
Department of Zoology, Faculty of Life Science, Jahangirnagar University, Savar, Dhaka..
Radiation, Postembryonic development, Bactrocera.
Institute of Food and Radiation Biology, Atomic Energy Research Establishment, Savar, Dhaka, Bangladesh.
Pest Management
The melon fly, Bactrocera cucurbitae, were collected from a stock culture maintained in the fruitfly laboratory of the Institute of Food and Radiation Biology, Atomic Energy Research Establishment, Savar, Dhaka, for the last fifteen years. Initially the flies were collected from the nature and a colony was gradually established in successive years. The adult insects were maintained in a controlled room temperature (29 ± 1ºC) with 75 ± 5 % RH. Soon after emergence, the adults were provided with sugar and water. One day after emergence, they were provided with regular food prepared by yeast, sugar, casein and water. The larvae were maintained in an artificial diet following Tanaka et al. (1969) with slight modification. The eggs of the melonfly were collected from 15-20 days and 35-45 days old age groups of parents. A batch of 50 eggs was used for each treatment and 4, 8, 12, 16 and 20 hours old eggs were selected for this purpose. The doses used were 2, 4, 6, 8 and 10 Gy of gamma radiation. All the eggs were incubated on a moist tissue paper. After 24 hours, the eggs were carefully observed under a binocular microscope and checked for hatching. The hatched and unhatched eggs were counted and recorded. The experiment was replicated thrice. The mortality of the eggs was assessed in terms of the egg hatched to calculate LD50 values from the data. For larval mortality test, batches of 50 Ist instar larvae were collected from the stock culture and were separately exposed to 1, 5, 10, 20, 30, 40 and 50 Gy doses of radiation. All the larvae were maintained in an artificial diet as mentioned before. The larvae were regularly observed until pupation and thereby determined the duration of larval period. The number of adults emerged was recorded and the percentage of adults emerged was calculated. Similar procedure was followed for the 2nd and 3rd instar larvae. The pupae of age groups 24, 48, 72, 96 and 120 hours were collected from the stock culture and exposed to 10, 20, 30, 40, 50, 60, 70, 80, 90 and 100 Gy doses of radiation. After radiation, the pupae of each treatment as well as control groups were separately caged and carefully observed for adult emergence. The number of adults emerged from each treated and untreated groups was recorded separately. The mortality was assessed in terms of the adult emergence. In all cases, the experiments were replicated thrice and there was always a control batch. The effects of different radiation doses on the larval period, pupal period, pupation and adult emergence were calculated by statistically analysis of variance. The means of the larval period, pupal period, pupation and adult emergence were tested using a Duncan’s multiple range test. A Co60 irradiator (strength 16,000 Ci, June 1996 of Canada limited) was used for the radiation treatment. The irradiator was used at a dose rate of 50kr/hr (1 Ci = 3.70 x 1010 Bq).
Bangladesh J. Zool. 34(1): 87-94, 2006
Journal