Abstract
The cedar web-spinning sawfly, Cephalcia tannourinensis (Hymenoptera: Pamphiliidae) is considered a major defoliator of the cedar forests in Lebanon. In the early 1990’s, a severe damage of the Tannourine Hadath El-Jebbeh cedar forest was caused by the sudden outbreak of this insect. The insect has a complex life cycle with two types of diapause: annual diapause and multiple years diapause. The present study aimed at studying soil characteristics and their influence on the survival and diapausing cycles of C. tannourinensis prepupae. Different soil samples collected from three different cedars forests in Lebanon were incubated with prepupae of C. tannourinensis under laboratory conditions. The effect of soil origins and properties on prepupal mortality, annual diapause and multiple years diapause cycles were analyzed. The influence of soil moisture and soil temperature on prepupal development was studied separately through two constant temperatures and three constant soil moisture levels. Prepupal mortality was found to be highly correlated with soil properties and types. Prepupae survived well in soil coming from Tannourine and Bcharry followed by Chouf. However mortality was almost 100% in the two reference soils sand and peat. Diapause cycle was strongly correlated with temperature while the effect of moisture was mainly on the prepupal survival. Key words: Cephalcia tannourinensis, soil moisture, soil temperature, annual diapause, multiple years diapauses.  
Highlights
The inffluence e of so oil prop perties s on th he deve elopme ent of Cephalcia tannouri rinensiis Chev vin
C. tannourinensis larvae as well as the annual and multi annual diapause development of this insect and (ii) understand the relation between soil temperatures and soil moisture vis-à-vis the development of the prepupae of C. tannourinensis
(viii) pH and electric conductivity (EC): A total weight of 10 g of each air dried soil sample were transferred into a 50 ml falcon tube, 25 ml of distilled water were added to each tube and shaken on an electric shaker for 30 min
Summary
The Cedar of Lebanon covered a large area of Lebanon’s mountains. 1990 and 1999, the intensity had been increasing in Tannourine-Hadath El-Jebbeh cedar forest located in northern Lebanon and has caused intense defoliation of over 600 ha. The danger of the spread of this insect to other cedar forests in Lebanon and the Mediterranean region led to the initiation of a UNEP/GEF project entitled “Integrated. Management of Cedar Forests in Lebanon in Cooperation with Other Mediterranean Countries” that aims to develop an action plan for integrated management of forests including assessment of insects in cedar forest in the Mediterranean region with particular emphasis on the Tannourine-Hadath El-Jebbeh cedar forest. The causes of Cephalcia outbreak in the forest of Tannourine-Hadath El-Jebbeh are still not known. C. tannourinensis larvae as well as the annual and multi annual diapause development of this insect and (ii) understand the relation between soil temperatures and soil moisture vis-à-vis the development of the prepupae of C. tannourinensis
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