Nasonovia ribisnigri (Mosely) is one of the most important pests of the lettuce plant and it was reported for the first time in Ahvaz in 2008. In order to investigate the dominant species of its natural enemies and their population fluctuations, sample were taken arbitrarily from fifty plants twice a week during the growing season in 2010-2012. In this study, ten species of predators, three species of parasitoids and two species of hyperparasitoids were collected and identified. Hoverflies with a relative frequency of 55% were the dominant predators. Peaks of lacewings and subsequently ladybird beetles were more coincident with peaks of aphid population in mid-March in the first year of studies. But their densities in the second year were very low. Also, hoverflies and parasitoids were mainly observed in the high densities in late March-early April, in both years. Regression analysis indicated that populations of aphids were mainly affected by ladybird beetles and lacewings in the first year of study, as well as by ladybird beetles, hoverflies and parasitoids in the second year. Therefore, additional studies are required for further evaluation on the potential abilities of these natural enemies being a good candidates for the future biological control programs.  

Keywords: Nasonovia ribisnigri, natural enemies, population fluctuation, multiple regressions, Biological control

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