Studying the causes of Lebanese cedar Cedrus libani A.Rich. dieback in the cedar-fir protected area in Slunfeh - Syria

This study was carried out in the cedar-fir protected area in Slunfeh – Syria 2022-2023 and aimed at studying the distribution and spread of the Lebanese cedar Cedrus libani A.Rich is in the Reserve and determine the causes of the death of the tops of these trees. The method of squares was adopted to determine the number of trees, 10 squares with dimensions of 20x20 M2 were selected on the eastern and southern slopes where the spread of cedar is concentrated. The results showed that the relative abundance and density of Lebanese cedar per hectare on the southern slope was the hign compared to companion species, with relative abundance reaching 20.2% and density of 883.33 trees per hectare. On the other hand, only the Juniper Juniperus drupacea exceeded the Lebanese cedar in relative abundance and density on the eastern slope of the Reserve, as the density of the Juniper reached 478.57 trees per hectare compared to 267.86 trees per hectare for the Lebanese cedar with a relative abundance of 9.4%. To determine the causes of the death of tree tops, the presence of the Lebanese cedar moth (Dichelia cedricola Diakonoff Lepidoptera: Tortricidac) was recorded for the first time in Syria on the Lebanese cedar trees. The symptoms of infection was described, the most important biometric measurements of the various phases of the insect were recorded, and also studied the insect's life cycle in the field, where the insect is active (in its various stages) from April to November of 2022. The larvae feed on needle leaves and new shoots, and use the needle leaves for nesting and roosting, which causes the needles to fall off and damage the tree, which requires control. A fungal infection was also recorded that causes the death of tree tops and young branches.The symptoms of infection were determined in the field. The symptoms were represented by the redness of the needle leaves of the tree tops and falling from the top of the crown to the bottom.When studying the infected needle leaves under the magnifier, the symptoms of infection were represented by the formation of black vessels on the dead leaves and tops. The symptoms of the beginning of infection on the green leaves appeared under the magnifier in the form of yellow spots that gradually turn red and end with the drying and death of the leaves. The causative fungus was isolated, purified and studied microscopically, the conidial spores appeared small oval or cylindrical curved two-celled with rounded ends formed on simple lateral branches, thus the fungal disease was defined as leaf blight and Apex and is caused by the fungi Cytospora cedri and Diplodia sapinea. An analysis of the soil of the Reserve was conducted, the results showed that the soil with a clay texture and its content of major nutrients on the eastern and southern slopes of cedar-fir protected area is similar, noting the low nitrogen content of the soil and its high potassium content in all samples