Effect of Humidity on Fecundity and Egg Incubation of Frankliniella bispinosa and Frankliniella occidentalis (Thysanoptera: Thripidae)

Abstract

Environmental factors are hypothesized to account for spatial and temporal differences in Florida in the abundance and distribution of the native thrips species Frankliniella bispinosa (Morgan) and the invasive Frankliniella occidentalis (Pergande) (Thysanoptera: Thripidae). Laboratory experiments were conducted at a constant temperature of 23 ± 1 °C to investigate the effects of humidity on the fecundity and egg incubation of F. bispinosa and F. occidentalis. Adult thrips were allowed to oviposit on green bean (Phaseolus vulgaris L.; Fabaceae) pods. Eggs were maintained at relative humidity treatment levels of 40 ± 5, 55 ± 5, 70 ± 5, and 80 ± 5%. Fecundity and time of egg hatch were determined every 12 h. Results showed that F. bispinosa had a higher fecundity and a shorter time to egg hatch compared with F. occidentalis at higher humidity levels. These results partially explained patterns of abundance and distribution of F. bispinosa and F. occidentalis in Florida. When relative humidity was high in summer and fall, populations of F. bispinosa were abundant and population levels of F. occidentalis were very low. Management strategies for F. bispinosa and F. occidentalis can be improved to accommodate the biological differences.