Population dynamics of Dialeurodes citri Ashmead and its predator Clitostethus arcuatus Rossi in the citrus region of Chettia (North-West of Algeria)

Abstract: Citrus whitefly Dialeurodes citri (Ashmead) is a major pest in the Mediterranean basin. It is expanding in Algeria and is now a serious problem for citrus plantations. The study was conducted from July 2013 to June 2014 at a Clementine orchard in the region of Chettia (North-West of Algeria). Adult and larval populations were sampled from infested shoots. Whitefly adults and their predators were caught using yellow sticky traps. The analysis of the temporal fluctuations of the populations revealed the presence of two flight periods corresponding to the two generations (spring generation, greater autumnal generation with more than 80 adults/branch/fortnight). Population densities are highest on autumn sap and lower on summer sap. The high larval mortality rate (40% to 60%) is due to temperature differences between day and night, differences of 16.7 °C were recorded (19.6 °C at night and 35.8 °C the day in November 2013). Despite the presence of a significant number of predator ladybird adults coinciding with the two periods of D. citri increase, the biological regulation activity of Clitostethus arcuatus Rossi remains low and D. citri populations are still causing considerable damage to Clementine.