SALMA AKTER1*, RAZZAB ALI1, MUNJURI AKTER1 and MD. RAFIQUL ISLAM2
1Department of Entomology, Sher-e-Bangla Agricultural University, Dhaka-1207 and 2Department of Biotechnology, Patuakhali Science and Technology University, Patuakhali, Bangladesh.
*Corresponding author’s Email: shammi1555@gmail.com
ABSTRACT
The study was conducted at the Laboratory, Department of Entomology, Sher-e-Bangla Agricultural University, Dhaka, Bangladesh during the period from May 2011 to October 2011 to find out the economically viable mass rearing technique of the Trichogramma evanescens Westwood egg parasitoid on parasitizing the eggs of Lepidopterous insect pests rice moth, Sitotroga cerealella. The experiment was also undertaken to find the effect of different factors on Trichogramma’s biology and parasitization. The experiment was laid out in Complete Randomized Design (CRD) with four replications. Among the three grains (wheat, maize and rice) used in rearing Sitotroga cerealella, wheat grains showed the best result. Adult Sitotroga taken 22 days for its emergence from wheat grains and 23 days from both maize and rice grains. In case of feeding, Sitotroga cerealella larva preferred the wheat grains which results 290.30gm weight loss of wheat grains after one month of adult emergence and 580.30gm of weight loss of wheat grains after two months of adult emergence, but in maize and rice grains 191.50 gm and 100.80 gm of weight loss was observed respectively. While after two months of adult emergence of Sitotroga cause 381.30gm and 220.80gm of weight loss in maize and rice grains respectively. The fecundity performance of Sitotroga was highest in wheat grains (3128 mg of rice moth eggs was collected) than that of maize (550.80 mg) and rice (29.25 mg) grains. Hence wheat grains were preferable to rice moth than other grains. For rearing of Sitotroga, sterilization of wheat grains with hot water was found better than Brian solution treatment, normal water treatment and no sterilization. From the hot water treated grains 1200.00 mg of Sitotrogaeggs was collected, while 971.80 mg, 893.80 mg and 73.30 mg of egg were collected from Brian solution treated, normal water treated and non-treated grains respectively. For mass rearing of Trichogramma egg parasitoid freshly laid host (Sitotroga) eggs were better than preserved host eggs. In fresh host eggs Trichogramma egg parasitoid required 7.25 days to complete lifecycle where adult longevity, larval period and pupal period was 3.25 days, 2.25 days and 2.50 days respectively. But Trichogramma required 12.50 days when reared in 10 days preserved host eggs, in this case adult longevity, larval period and pupal period was 3.50 days, 4.75 days and 4.50 days respectively. So the lifecycle of the Trichogramma egg parasitoid on fresh laid host eggs was shorter than that of refrigerated host eggs depending upon the duration of refrigeration. Larval and pupal period also showed the similar trend on fresh and old host eggs. But adult longevity showed no significant variations on the different age of host eggs. As well as rate of parasitization of Trichogramma on fresh laid host eggs was also maximum (90.00%) than that of refrigerated host eggs (84.33 to 54.67%) depending upon the duration of refrigeration. Grains (wheat, maize and rice) used in rearing the host (Sitotroga) showed significant variations on the biology and parasitization of the parasitoid. The lowest period of 7.75 days were required to complete the life cycle of the parasitoid when the host eggs reared on the wheat grains. Whereas it required longer duration of 9.00 days and 8.25 days to complete the life cycle of the parasitoid in the host eggs reared on the rice grains and maize grains respectively. Similarly highest percentage of parasitization (92.50%) and adult emergence (95.75%) of Trichogramma were found in case of host eggs those reared in wheat grains. So for rearing Trichogramma egg parasitoid freshly laid host eggs reared in wheat grains showed the best result.
Keywords: Mass rearing, Sitotroga cerealella and Trichogramma evanescens.