Population dynamic monitoring of Phyllocnistis citrella (Lepidoptera: Gracillariidae) using immature stages sampling and male moth pheromone-baited traps

The citrus leafminer (CLM) Phyllocnistis citrella Stainton (Lepidoptera; Gracillariidae) is an important citrus pest. The population dynamic was monitored to assess the infestation state during summer-autumn seasons in a citrus-growing area of Algeria (Mitidja). The densities were estimated using immature stages sampling and male moth catches in pheromone-baited traps. The analysis of both methods showed that the presence of the CLM did not differ significantly between years but differs significantly between months. The monitoring of the population revealed that the incidence of this pest has considerably decreased compared to its first introduction in the area. The insect has developed 4 generations for both years considered; 2 in summer and another 2 in autumn. The mean density of CLM per leaf recorded was 1.42 in 2017 and 1.24 in 2018. The number of moth caught in pheromone-baited traps showed an important density and was predictive for the immature stages’ population. No significant relationship was found between moth catches and larval densities during the successive years studied. However, a significant relationship was found between larval densities and infested flushes on one hand, and on the other hand, between total flushes density and flushes infested. The moths catches using pheromone-baited traps could present a complementary variability source to help measure population and predict infestations. However, they do not necessarily reflect the actual immature stages densities.