Density-Dependent Demography and Mass-Rearing of Carposina sasakii (Lepidoptera: Carposinidae) Incorporating Life Table Variability.

Abstract

Carposina sasakii Matsumura is one of the most destructive fruit-boring pests of pome and stone fruit trees in eastern Asia. Because larvae complete their development inside a single fruit, larval density per fruit is a critical factor in their survival, development, and fecundity. The effect of larval density was examined to determine the ideal density for devising an economic and sustainable mass-rearing system for harvesting of C. sasakii. Mass production of insects of the same age of a specific stage is not only important in biological control, but also in pheromone extraction, culturing of entomopathogenic nematodes and fungi, etc. Life history data for six larval densities (1-5, 6-10, 11-15, 16-20, 21-30, and 31-40 larvae/apple) were collected at 25.5 ± 0.5°C, 75.0 ± 5.0% RH, and a photoperiod of 15:9 (L: D) h. Data were analyzed using the age-stage, two-sex life table. The results showed that the highest preadult survival rate (42.00%), fecundity (104.70 eggs), and population parameters (intrinsic rate of increase r = 0.0718 d-1, net reproductive rate R0 = 23.03 eggs, and finite rate of increase λ = 1.0744 d-1) were observed at a density of 1-5 larvae/apple. However, when the rearing costs and production rate were considered, the density of 16-20 larvae/apple was the most economical for mass-rearing C. sasakii in order to achieve a daily harvest rate of 1,000 pupae (from 273 apples per day). To ensure the sustainability of the mass-rearing system, we included the life table variability in the harvesting strategy.