Seasonal Variation in Snail Abundance and Distribution at Different Citrus varieties on Sharkia Governorate

This study investigated the seasonal population dynamics (horizontal and vertical distribution) of the snail Theba pisana (Müller) under field conditions of three citrus varieties at Sharkia Governorate, Egypt, during 2022-2023 growing season. The research examined both horizontal (0.5m, 1m, 1.5m from tree trunk) and vertical (0-1m, 1-2m, >2m) distribution patterns on navel orange (Citrus sinensis), balady mandarin (Citrus deliciosa), and ponkan mandarin (Citrus reticulata). Horizontal distribution analysis demonstrated an inverse relationship between distance from tree trunk and snail density across all varieties, with highest populations recorded at 0.5m followed by 1m. The lowest population was at a distance of 1.5 m from the tree trunk. Peaks of seasonal populations occurred during spring month (March-May) for balady mandarin and navel orange and in March for ponkan mandarin. All varieties exhibited minimal population during summer months (July-September). In respect to vertical distribution, all varieties showed a clear preference for the middle canopy zone (1-2m), followed by lower zone (0-1m) while, the lowest snail densities were consistently observed in the upper canopy (>2m). Seasonal fluctuations showed peak populations during summer months (June-August), with lowest population during winter. A significant difference in population density (horizontal and vertical distribution) between balady mandarin and both navel orange and ponkan mandarin. However, no significant difference was observed between navel orange and ponkan mandarin. Balady mandarin supported the highest overall population density followed by navel orange and ponkan mandarin.