Development of Bradysia odoriphaga (Diptera: Sciaridae) as affected by humidity: an age-stage, two-sex, life-table study

The gnat Bradysia odoriphaga Yang et Zhang (Diptera: Sciaridae) is an important pest of Chinese chive (Allium tuberosum Rottler ex Sprengel). Although B. odoriphaga outbreaks are thought to depend on soil humidity, the mechanism by which humidity affects the outbreaks is poorly understood. In this study, the life history of B. odoriphaga (Diptera: Sciaridae) on Chinese chive was studied with an age-stage, two-sex life table and with relative humidity (RH) at 50, 60, 70, or 80 %. The developmental time of eggs and larvae, total preoviposition duration, and total preadult duration were longer at 50 % RH than at higher RH values. The mean total preadult duration was 34.16 days at 50 % RH and ranged from 27.34 to 31.81 days at 60-80 % RH. The mean fecundity was significantly higher at 70 % RH (as high as 62.88 eggs/female) than at 50, 60, or 80 % RH (from 33.41 to 50.52 eggs/female). The intrinsic capacity of increase (r), net production rate (R (0)), and finite rate of increase (lambda) increased as RH increased from 50 to 80 %, and mean generation time (T) showed the opposite trend. This study provides insight into the phenology of B. odoriphaga and shows that high RH promotes outbreaks of B. odoriphaga.