This work was carried out to investigate the effect of infestation with two diaspid, Florida red scale, Chrysomphalus aonidum (L.) and Black parlatoria scale, Parlatoria ziziphi (Lucas) (Hemiptera: Diaspididae) flowers oil content, fruit characters and yield of sour orange at Kafr EL-Sohaby, Qalubyia Governorate during 2008/09 and 2009/10 seasons.
A delay was observed in inflorescence emergence date between uninfested and infested ones over the two seasons. Mean reduction of infestation with C. aonidum and P. ziziphi of inflorescences per meter (67, 75.5 %), flowers yield (72.75, 84.85 %), and flowers' volatile oil content (35.25, 69.4 %), in 2008 - 09 & 2009 -10 seasons, respectively. The reduction of the volatile oil, (physical and chemical properties) and the main components of the volatile oil of sour orange.
The results showed an increment in the reduction percentage of the volatile oil content and effect on the physical and chemical properties of volatile oil. In the same trend the main components percentage in the volatile oil were affected of the deferent types of the scale insects specially linalool and linalyl acetate. There were a heavy loss of yield per tree (39.49, 41.07 %), due to infestation by C. aonidum and P. ziziphi, respectively. While it was a low decreasing as a result of infestation by C. aonidum and P. ziziphi in fruit weight (2.58, 2.74 %), however height of fruit (3.83, 3.7 %) and diameter of fruit (3.21, 3.34 %) over the two seasons respectively. On the other hand, there were a low loss due to infestation of C. aonidum and a heavy decrease in infestation of P. ziziphi. In fruit juice acidity (3.54, 10. 45 %), percent of protein (4.48, 14.15 %), percent of total sugars (4.45, 18.15 %) and percent of vitamin C (4.45, 7.24 %) in 2009 and 2010 seasons, respectively.