Olive leaf gall midge (Dasineura oleae Angelini, Diptera, Cecidomyiidae): determination of olive tree infestation rates and quantification of parasitism by indigenous parasitoids

Abstract

The olive leaf gall midge is a serious insect pest on olive trees in the Palestinian Territories. It induces galls on the leaves and other vegetative organs of olive trees causing reduction in the yield. The main objectives of the present study were to determine the infestation rate with Dasineura oleae on olive trees cultivated over variable altitudes in the Palestinian Territories, to identify the indigenous parasitoids of D. oleae and to determine the overall rates of parasitism by the identified parasitoids on D. oleae. Results indicated that the infestation rates with D. oleae varied significantly depending on the altitudes of sampling sites ranging from 12.1 to 52.7% at 635 and 229 m above sea level (a.s.l.), respectively. Two species of indigenous hymenopterous parasitoids on D. oleae were identified: Platygaster oleae Szelenyi (Platygastridae) and Zeytinus hatayensis Doganlar (Eulophidae) (new record for the Palestinian Territories). The overall rates of parasitism by the identified parasitoids varied significantly with the altitude of the sampling sites from 12.6% (Assira El-Shamalieh, 635 m a.s.l.) to 55.5% (Aljarochia, 102 m a.s.l.). Partitioning of the overall rates of parasitism between the identified parasitoids indicated that P. oleae was found at all sampling sites (82 to 635 m a.s.l.) with proportions of 60.8–100%, whereas Z. hatayensis with proportions of 0–39.1% and was not found at altitudes above 492 m a.s.l. The overall results suggest the use of P. oleae and Z. hatayensis in biocontrol of D. oleae in the Palestinian Territories.