The Population Dynamics of Black Bean Aphid Aphis Fabae (Hom., Aphididae) and its Parasitoid Wasp Lysiphlebus Fabarum (Hym., Braconidae) on Two Broad Bean Varieties in Ahvaz

Aphis fabae is the most important pest of agricultural crops. In this research، the population dynamics of black bean aphid، Aphis fabae، was studied on two broad bean varieties (Barkat and Shakh Bozi) at College of Agriculture field station، Shahid Chamran University، Ahvaz، Southwest of Iran in during 2006-2007. Different sampling methods such as leaf samples and yellow water traps were used. The seasonal parasitism rate of black bean aphid، A. fabae، by parasitoid wasp Lysiphlebus fabarum was also recorded. The results indicated that A. fabae was emerged in late November; then the population density gradually increased in mid January and peaked in mid March and then decreased in late April. Statistical calculations indicated that the population density of A. fabae on broad bean Barkat variety was higer than Shakh Bozi variety. The activity of the parasitoid wasp L. fabarum on A. fabae started from late November. The mean scores of parasitism percentage on broad bean Barkat and Shakh Bozi varities were 25. 28% and 20. 51%، respectively. The maximum parasitism rate by L. fabarum was at the same time with pest population peak in mid March، it played an important role in the biological control of A. fabae.