Experiments were conducted in a private farm cultivated with sugarbeet crop (Top cv.) for the two successive seasons of 2013/2014 and 2014/2015 to determine the economic damage threshold levels of Pegomia hyo-scyami Curtis (Diptera: Anthomyidae) under field conditions in Nobaria region, El-Behaira Governorate, Egypt. The results showed that the relationship between the yield of sugarbeet and the infestation of sugarbeet fly, Pegomia hyo-scyami Curtis (Pegomyia mixta Vill.) was negative, which is means that an increase in larvae numbers caused a decrease in roots yield and vice-versa.
In both seasons, Pegomyia hyo-scyami Curtis larvae registered two seasonal peaks of abundance that occurred in February and March.
The determined economic threshold level for Pegomia hyo-scyami Curtis was 19 larvae / plant and the economic injury level was 22 larvae / plant in the first season. But the values were 21 larvae / plant and 22 larvae / plant, in respect, in the second season.