Olive tree is one of the most cultivated trees over the Palestinian territories, it is considered as the mainstay of rainfed agriculture in Palestine. Recently and due to the impact of the global warming, olive trees were infected with an outbreak of many pests and pathogens. In the last decades, both olive fruit fly, Bactrocera oleae (Diptera, Tephritidae) and peacock leaf spot, Spilocaea oleagina were reported with an unusual percentage of infections over the olive trees. During 2015-16, and throughout the field surveys to investigate any unusual diseased symptoms on olives; some trees exhibited pale yellowing on the newly formed branches, symptoms associated with viral infections such as OLYaV. Some other trees were noticed to get yellowing and later on developed branch dieback and stem canker and cracking syndromes. When the outer bark was removed, the affected tissue appeared dark brown, in contrast to the yellowish green of healthy inner bark. These symptoms were observed on both young and old trees in the northern part of Palestine. Field and laboratory investigation revealed a heavy infestation with larvae of Resseliella oleisuga Targ. (Diptera : Cecidomyiidae). The infestation rate reported ranged from 75 to 92 in some olive orchards. Pathogens were isolated and identified based on cultural morphology. Climate changes due to the global warming might be the cause of this outbreak; probably due to the changes in the environmental conditions favoured by the insects. To our knowledge, this is the first time this insect was reported to be widely spread of olive trees and causing damage in Palestine. In this study, several associated primary, secondary and saprophytic diseases were detected from the infected samples. Mainly Botryosphaeria spp., Alternaria solani Sor., Aspergillus niger v. Tieghem, Cladosporium herbarum Fr., Fusarium solani (Mart.) App., Penicillium digitatum Sacc., Penicillium italicum Wehmer, Rhizopus stolonifer (Her.) Vuill.