Population trends of olive leaf midge Dasineura oleae Loew (Diptera: Cecidomyiidae) and the effect of some insecticides on the midge and its parasites in Amman District

A survey of olive leaf midge (Mar 1996- Feb 1997) showed that it was widely distributed in Jordan in all economically olive planted orchards which were visited. The highest percentages of infestation were recorded in Jeash (62%) and Mahis (55%). The lowest percentages of infestation were recorded in Shubak (6%) and Karak (5%). The susceptibility of six cultivars to attack by the olive leave midge have been studied in Baqa'a orchard. These cultivars were: Nabali-Mohassan, K18, Grossa -De, Sanfransisco, Telmisani, and Frantoio. This study showed that the cultivars Frantoio, Sanfransisco, and Telmisani were highly susceptible to the midge attack, while the lowest susceptibility appeared in the two cultivars Nabali Mohassan and Grossa-De. Seasonal development of different stages of olive leaf midge, showed that the peak of larval population in both leaves and twigs was in mid September up to ealy October, 1996, but the peak of pupal population was in late March up to early April, 1996. The highest numbers of emerged adults from the galls was in mid-May, 1996. These numbers of developmental stages showed that the midge has one generation per year (univoltine) in both infested leaves and twigs. The highest larval mortality was between mid-July up to mid-Audust, 1996, and the highest pupal mortality-in mid-June, 1996. The main mortality factors were climatic conditions (temperature and relative humidity), and natural enemies, especially the endoparasitoid Platygaster oleae Szelenyi (Hymenoptera: Platygastridae). Four parasites were reared from immature stages of olive leaf midge collected form olive trees in Amman district. These parasitoids were identified as: Platygaster oleae Szelenyi, Aprostocetus sp., and other two unidentified parasitoids. Ten insecticides were evaluated for the control of olive leaf midge using three sprays during 1996. In the first spray on April 1, all tested insecticides gave significant results in the midge compared to contol treatment after one week of insecticides application. Nomolt and Chlorofet showed the highest larval and pupal mortality of the midge, and Lannate showed the highest parasitoids mortality but with no significant differences. In the second spray on July 3, all tested insecticides showed significant effect compared to control treatment. Nomolt, Chlorofed, and Dimilin showed the highest larval mortality of the midge. In the third spray on August 5, Decis-D, Diazinon, and Chlorofet showed the highest larval mortality. In the last two sprays the effect of tested insecticides was not evaluated against the pupae and parasitoids of olive leaf midge due to low numbers during these periods