Influence of the egg parasitoidPlatytelenomus busseolae [Hym.: Scelionidae] on the population ofSesamia nonagrioides [Lep.: Noctuidae] in central greece

The egg parasitoid,Platytelenomus busseolae (Gahan) (Hymenoptera: Scelionidae) was recorded from egg masses of the corn stalk borer,Sesamia nonagrioides (Lefebvre) (Lepidoptera: Noctuidae) on maize in the area of Istiaea, Central Greece. Natural parasitism was studied during the years 1986, 1987. A total of 3,382 egg masses, containing 205,227 eggs, was collected from corn fields. Parasitized eggs were found from end July to mid-October. In 1986. 76.2% of the egg masses and 42.8% of all eggs were parasitized, while in 1987, respective values were 27.6% and 12.9%. The inferior performance of the parasitoid in 1987 may be due to the unfavorable winter and summer conditions. Parasitism decreased when the host population was at its peak, but it increased again within 1 to 3 weeks. A small percentage of egg masses was completely parasitized (9.5% and 4.7% for the 2 years respectively). In 1987, the sex ratio, ♀♀/♂♂ was 1.5: 1 and 26.2% of the egg masses produced only ♂♂. Mated ♀♀ produced 3 times more ♀♀ than ♂♂. It seems that the parasitoid, under favorable weather conditions, can play a significant role in the control of the corn stalk borer.