Laboratory Study of the Effect of Some Factors on the Parasitoid, Psyttalia concolor (Szépligeti), of the Olive Fruit Fly

Abstract

The main objective of this study was to study the effect of some influencing factors on Psyttalia concolor (Szépligeti) (Hymenoptera: Braconidae) parasitism, which is one of the most important insect parasitoids used in biological control of the olive fruit fly. The study was carried out at the Biological Control Studies and Research Center, Faculty of Agriculture, Damascus University. Results obtained indicated that the parasitoid prefers the third larval instar, followed by the fully-grown larvae. The effect of olive (Olea europaea L.) fruit size on parasitism rate was quantified within one olive cultivar (Kaisi) and across four different olive cultivars (Mawi, Istanboli, Sorani and Kaisi, in increasing order of fruit size). Parasitism was examined under two different host distributions: variable distribution in which insect host density increased with decrease in olive fruit size; and uniform distribution in which insect host density was more or less similar across olive fruit sizes. The results obtained showed that the parasitism rate decreased as the size of the olive fruit increased. In addition, parasitism rate was influenced by the olive variety, olive fruit size and the age of the insect host larvae. Furthermore, the parasitoid preferred the third larval stage, thus it is recommended to release the parasitoid in commercial olive orchards at the time when the third larval stage of the olive fruit fly is prevalent, and such date could vary from one region to another. Keyword: Parasitoid, natural enemies, Kaisi variety, olive, Psyttalia