Seasonal fluctuations of fiorinia date scale, Fiorinia phoenicis Balachowsky (Hemiptera: Diaspididae) populations on date palm trees at Qalubyia Governorate, Egypt

The present study was carried out throughout two successive years (2009–2011) in Qalubyia Governorate to determine the seasonal activity of fiorinia date scale, Fiorinia phoenicis Balachowsky (Hemiptera: Diaspididae) on date palm. The obtained results showed that, both nymphal and adult stages have two periods of seasonal activity per year. The 1st period of nymphal activity occurred in autumn season peaked in early December in both years with mean numbers of 749 and 838 nymphs/10 leaflets, respectively. The 2nd period of nymphal activity occurred in summer season peaked in early July (1124 nymphs/10 leaflets) in the 1st year and early June (1172 nymphs/10 leaflets) during the 2nd one. The 1st period of adult activity was recorded during autumn–winter seasons with one peak in early February (2385 and 2921 adults/10 leaflets) in the 1st and 2nd year, respectively. The 2nd period of activity was determined during summer season peaked in early July (2908 adults/10 leaflets) in the 1st year and early June (3664 adults/10 leaflets) in the 2nd one. Distribution of insect population on different strata of date palm leaflets was significantly different from one stratum to another, the middle stratum received the highest number of insects, followed by apical and basal strata during the two studied years, respectively. On the other hand, the duration of seasonal activity for both nymphal and adult stages was affected significantly with the tested weather factors (daily mean maximum and minimum temperatures and % RH). The combined effect of the tested factors on the nymphal activity ranged 58.2–74.8% in the 1st period of activity and 66.9–74.8% in the 2nd one for the 2 years, respectively. In addition, the combined effect on the adult activity ranged 53.9–76.3% in the 1st period and 84.9–87.9% in the 2nd one for the 1st and 2nd year, respectively.