Factors influencing the seasonal fluctuations of two insect pests of pomegranate Punica granatum L. (Punicaceae) under oasis ecosystem in Tunisia

The carob moth, Ectomyelois ceratoniae, and the pomegranate butterfly, Deudorix livia, are the most serious lepidopteran insect pests of the pomegranate in Tunisia. However, their population dynamics and competition under oasis conditions are not well understood. A 3-year study was conducted to investigate the population dynamics of those pests in the oasis of Gafsa (southwest of Tunisia). A correlation between incidence of E. ceratoniae and D. livia populations and climatic factors was also determined. Moreover, their damage to four pomegranate varieties (Guebsi, Tounsi, Zehri, and Baldi) was assessed. Interspecific competition between E. ceratoniae and D. livia was studied. Results showed that both E. ceratoniae and D. livia developed three annual generations. Furthermore, results revealed that E. ceratoniae had the highest infestation rate during the first weeks of pomegranate maturity (36%). However, with advances in maturity, D. livia became the major pest infesting pomegranate fruits (49%). In addition, results showed that climatic factors have a significant influence on the population dynamics of E. ceratoniae and D. livia. Correlations studies revealed that there was a significant positive correlation between infestation caused by E. ceratoniae and temperature (r = 0.515). However, infestation by D. livia was correlated with humidity and precipitation (r = 0.393 and r = 0.401, respectively). Furthermore, Baldi and Zehri seemed to be the most infested varieties by D. livia and E. ceratoniae. However, Guebsi was the most resistant variety. Regarding spatial distribution of larvae, E. ceratoniae larvae were present in all studied varieties at immature stage, while D. livia larvae were absent. At the mature stage, D. livia larvae were 75% more abundant than E. ceratoniae larvae. Thus, results could be used for developing and implementing innovative integrated pest management programs against E. ceratoniae and D. livia in pomegranate orchards.