Abstract
The presence of deformations has been observed in different areas on the trunks of date palm trees, Phoenix dactylifera L., planted and used in the landscape of sites and streets in Riyadh, Saudi Arabia. This study was conducted on the trunks of date palms, to investigate their cases and identify factors that led to distortion. The study was done on street islands planted with date palm trees in five different districts of Riyadh city. Each island of the street was divided into three parts and twenty palm trees from each part were studied. This study showed that date palm tree trunks used in the landscape of the streets were affected by damage and deformity at different heights on the trunk. The percentage of deformed date palm trees' trunks in four studied districts reached (100%), while it was (70.3%) in the fifth "Al-Khozama" district. In all studied districts, most of the trunk's deformity of date palm trees started from the soil surface, and the length of the deformation area on the trunks varied among these districts. The highest value of the average length of the deformation area was (119.6 cm) while the lowest value was (28.7cm). The results also showed that the highest value of the percentage of deformation (length of deformed area/length of trunk) on the trunk was (11.46%), while the lowest value was (6.26%). In this study, various of fungous species (Macrophomina phaseolina, Fusarium oxysporum, Fusarium solani) were isolated, purified and defined. These fungi found on the leaf bases in most deformed areas were a result of high humidity leading to rot and decay. This study indicated that the distorted areas on date palm trunks could be due to the growth of lateral roots on the trunks, causing the separation of the leaf bases. The occurrence of this case is because of some irrigation systems used improperly and resulted in water reaching directly to the palm trunks.