Population fluctuation of poplar aphid, Chaitophorus populeti (Hom.: Drepanosiphidae) and its predators in the Chaharmahal-Bakhtiari province

Chaitophorus populeti (Panzer) is considered as an important pest of Populus alba in the Chaharmahal-Bakhtiari province. During 2000-2001, the population fluctuation of the aphid and its predators was studied in four different regions including Juneghan, Zayandeh-Rood, Baba-Heidar and Cheshmeh-Ali. Population sampling was carried out weekly in these regions by cutting four branches (length 30 cm) from four trees considering the four main geographical directions. Then the aphids and natural enemies in each branch were counted. The results indicated that the peak of aphid populations occurred on the first half of June of 2000 and second half of June of 2001, with the mean of 165 ± 8.8 and 184 ± 6.6 aphids per branch respectively. In these two years, the aphid population densities, as well as population densities in the four geographical directions were not statistically different (p>0/05). The predators of the aphid collected in the four studied regions included four species of ladybirds, one lacewing species, two species of bugs and one fly species. There was a significant correlation between the aphid population and its predators. The calculated determination coefficient (R2) between the aphid population and ladybirds, and between the aphid population and other predators were 0.78 and 0.48 respectively, in 2000; and 0.88 and 0.84 respectively, in 2001. In both years, the determination coefficient between the aphid population and ladybirds was more than that of between the aphid population and other predators in the four regions.