Eleven species of parasitoids were found to attack 7 species of wheat aphids in Iran. The Simpson's Index of diversity (D) used to compare the aphidiine diversity in various cereal crop systems in geographically different regions of Iran ranged from 0.197 to 0.488, depending on locality. There were significant differences among species diversities at different altitudes. The central highlands (1000-1500 meters above mean sea level) were the areas with the most diverse aphid parasitoid complex, differing significantly from that at lower and higher altitudes. We found that altitude explained about 10% of the cereal aphid parasitoid distribution pattern in Iran. Species of the genus Aphidius Nees were the most abundant and widely distributed. These were Aphidius rhopalosiphi De Stefani, Aphidius uzbekistanicus Luzhetski, Aphidius colemani Viereck and Aphidius matricariae Haliday. A. uzbekistanicus, Ephedrus plagiator (Nees) and Ephedrus persicae Froggat were encountered mainly on the plains at lower altitudes. Diuraphis noxia (Kurdjumov) was mainly recorded at higher altitudes in Iran along with its dominant parasitoid species, Diaeretiella rapae (MIntosh). The fact that Iran is close to the presumed area of D. noxia origin (Central Asian submountains) could be very important in further biological control efforts against this pest aphid. According to our results, Aphidius ervi Haliday is a very rare parasitoid of cereal aphids in Iran, which contrast with its high abundance in Europe and North America.
Field studies were conducted, in order to assess the seasonal occurrence and the spatial distribution of Aphidius colemani Viereck, Aphidius matricariae Haliday, Diaeretiella rapae (M'Intosh), Praon staryi Kavallieratos & Lykouressis and Praon volucre (Haliday), all parasitoids of Myzus persicae (Sulzer) on tobacco. The experiments took place in western Greece (Agrinion, Aitoloakarnania), during the 1996 and 1997 growing seasons, in an area of approximately 2.5 ha, where tobacco was the main crop. The experimental field was insecticide-free and tobacco leaf samples (from the upper and lower half of plants) were taken from June until September, in both years. The distribution of the species found was also represented and discussed. Generally, high M. persicae densities were recorded in August (mid-season) of both seasons. The mummification rate showed a specific increasing trend late in the season (August-September). In 1996, the percentage of mummification reached almost 61% at the end of the period, whereas in 1997 it remained at very low levels (<2%). The density of M. persicae was higher on the leaves collected from the upper part of the plants than on those from the lower part, but without significant difference. In contrast, the numbers of mummified M. persicae individuals were significantly higher on leaves collected from the lower part of the plants than on those from the upper part in both years. The relative abundance of the aphidiine parasitoid species differed between the two years.