Relative effects of larval diets for Corcyra cephalonica on moth emergence and egg production in mass- rearing systems

Mass rearing of the rice moth, Corcyra cephalonica Stainton is a key component in mass production of several entomophagous biocontrol agents, for use as the factitious host/prey in commercial insectaries. Improvements in the larval diets for mass rearing of C. cephalonica constitute one of the strategies to enhance the efficiency and economics of large-scale rearing. The present study compared the relative efficiency of four larval diets (maize alone, sorghum alone, maize+ millet and maize +sorghum) in C.cephalonica mass production. The total moth production (over eight weeks duration) was found to be significantly higher (1657/tray) for sorghum + millet, followed by sorghum alone (1638), followed in rank by maize + millet (1268) while maize alone was the least productive (828). The peak moth emergence for all the diets was in the fifth week, while the two superior diets(sorghum+ millet and sorghum alone) showed enhanced moth production during the fourth to sixth weeks. Further, the overall egg production per tray followed a different trend from the overall moth production, the maximum egg production (11.9cc/tray) being in sorghum + millet, followed by sorghum alone (9.8cc), compared to third position by maize + millet (9.5cc), while the least eggs (4.8cc) were obtained with maize alone. It was evident that the larval diets not only differentially influenced the total moth production but also the fecundity (egg production efficiency) of the moths. The egg production efficiency of moths was observed to be maximum in millet + maize ,closely followed by millet+ sorghum Overall, millet+sorghum diet could be reckoned as the most productive diet, based on the greatest egg production, although more moths were produced in sorghum or maize-millet treatments. Since millet also tends to be cheaper than sorghum or maize, millet+ sorghum diet may be more economical for Corcyra egg production in commercial insectaries. Further research on the hatchability of eggs from moths reared on the more promising larval diets and their nutritional quality as prey/host in multiplication of insect biocontrol agents is recommended