HOST DENSITY OF THE APHID BREVICORYNE BRASSICAE LINNAEUS (HEMIPTERA: APHIDIDAE) ALTERS THE BIOTIC POTENTIAL OF THE APHID PARASITOID DIAERETIELLA RAPAE (HYMENOPTERA: BRACONIDAE: APHIDIINAE) Page No: 4799-4805

By: Muhammad Jaffar Hussain, Muhammad Anjum Aqueel, Abu Bakar Muhammad Raza and Errol Hassan

Keywords: Diaeretiella rapae, host density, percent parasitism, adult emergence

Abstract: Parasitoids are the most widely used group of natural enemies in biological control programs of insect pests especially for aphid species. Among the aphid parasitoids, Diaeretiella rapae is one of the most important to parasitize the aphid species Brevicoryne brassicae. The present study was done under laboratory condition (25±2 ºC temperature and 65- 70% R.H.) to assess the biotic potential of D. rapae on B. brassicae. We used host densities of 10, 20, 40, 80 and 120 aphids per cage. For each host density only two couples of male and female of D. rapae were released. Results showed that the highest parasitism rate (40.95%) was observed at the lowest host density (10 aphids), while minimum parasitism (23.41%) was observed at the highest host density (120 aphids). Parasitism rates of 36.08%, 33.63% and 31.76% were observed in host densities of 20, 40 and 80 aphids, respectively. The percent emergence of adult D. rapae from each host density of 10, 20, 40, 80 and 120 aphids was 81.17%, 69.44%, 63.34%, 48.42% and 44.76% respectively. The coefficients of determination (R2) values for percent parasitism and adult emergence were 91.95% and 90.24%, respectively. Our f0069ndings revealed that an increase in host density decreased the parasitic potential as well as the percent emergence of the aphid parasitoid



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