Background and Objectives
In the recent years the phenomenon of dust increased in the environment, so has affected most agricultural products such as date palm. This study has been conducted in order to study on the effects of dust on date palm (Phoenix dactylifera L.) pollination and fruit set. The experiment was carried out in two growing seasons 2014 and 2015 in order to evaluate the effect of combined treatments including dust, rain and pollination on fruit set, parthenocarpic fruits and fruit abscission of 8-years old `Estamaran’ (‘Sayer’) date palms in the field. In addition, dust sediment manner on the flower and stigmatic surface in the simulated environment at the laboratory was studied.

Materials and methods
In each combined treatment in the field, all bunches of experimental trees was treated as replications. At the laboratory, simulation operation has been done by placing the flowers under binocular camera and operating the combined treatments using soft brush for dusting and pollination on the stigma, also manual hand spray was applied. A month after treatments, traits such as fruit set, parthenocarpic fruit and abscission percentage and dust sedimentation manner on the flower and stigma was studied. The data were analyzed statistically using the analysis of variance using MINITAB17 software.

Results and Discussion
Results showed that treatments had significant effects on the studied traits. Maximum obtained from pollination (66.11%) and minimum fruit set obtained from non-pollinated treatment (0.5%). In the other applied treatments, in spite of pollination, existence of one or two other factors and their operation order had different effects on fruit set. Combined treatments that included dust caused significant reduction in fruit set and led to the increase in fruit abscission. The maximum parthenocarpic fruit set observed in non-pollinated treatment (23.38%) with the significant difference in comparison to other treatments and the minimum parthenocarpic fruit produced by combined dust, rain and pollination treatment (0.48%). The maximum abscission was observed in the combined dust, rain and pollination treatment (83.82%) and the minimum abscission observed in pollination treatment (32.88%). The simulated operation results at the laboratory was approved and quiet similar to the results obtained from the field experiment, so the formation of dust insulator layer on the stigmatic surface inhibited most of the pollen grains for direct contact to the stigmatic surface. The obtained results from this research showed the negative impact of the dust on fruit set, so we conclude and suggest the repeat of pollination after the dust storm during date palm pollination.