Population dynamics of Fiorinia phoenicis (Hemiptera-Diaspididae) on date palm at Baharia Oases, Giza governorate, Egypt

Abstract

The population dynamics of Fiorinia date scale, Fiorinia phoenicis (Hemiptera-Diaspididae) was studied for two successive years (2012/2013 and 2013/2014) on date palm cultivated at Baharia Oases, Giza Governorate. The obtained results revealed that, Fiorinia phoenicis has three annual field generations on date palm peaked in June/July; September and November in the two years. The longest generation occurred in autumn with duration of 5 months at mean temp. and R.H (21.4ºC & 65.5%R.H. and 22.8ºC & 66.2%R.H.), for the 1 st and 2 nd year respectively, whereas the shortest one was found in late summer with duration of 3 months at mean temp. and R.H (26.3ºC & 66.0%R.H. and 27.8ºC & 64.8%R.H.), for the 1 st and 2 nd year respectively. The intermediate generation occurred in early summer with duration of 4 months at mean temp. and R.H (22.8ºC & 63.4%R.H. and 24.9ºC & 63.6%R.H.) for the 1 st and 2 nd year, respectively. The generation size varied in the two years, the autumn generation is the largest one (12259.8 & 12153.4 insects), for the 1 st and 2 nd year respectively, followed by late summer generation (8184.2 & 7430.4 insects), for the 1 st and 2 nd year respectively), while early summer generation was the lowest one (6688.3 & 7422.1 insects), for the 1 st and 2 nd year, respectively. The population of F. phoenicis was found to be distributed at random on the date palm fronds especially the older ones. The cardinal directions of the date palm received similar portions of insect population except for the south direction which received the highest portion of insect population (26.8 & 28%), for the 1 st and 2 nd year respectively, and become relatively warmer and preferred for infestation than the other side's which received lesser and apparently similar portions of insect population (25.1 , 23.9% & 23.8, 24.3 % and 24.3 , 23.8 %), for East, West and North directions (the 1 st and 2 nd year),respectively. The distribution of F. phoenicis population on the different parts of the date palm leaflets varied, as the middle stratum received the highest portion of insect population (40.0 & 43.4 %) followed by basal stratum (34.3 & 33.3%) and apical stratum (25.7 & 23.3%) for the 1 st and 2 nd year, respectively. On the other hand, the insect activity was significantly affected by the daily mean minimum and maximum temperatures as well as % R.H. The changes in the half monthly counts of population, which were affected by the combined effect of these factors, which ranged (61.6 & 72.5% and 59.4 & 66.7%), for nymphs and adults (the 1 st and 2 nd year, respectively). So, the annual pruning of date palm and offshoots by removing the infested old fronds (lower fronds) is necessary for reducing the insect population and to save the date palm and dates from infestation by F. phoenicis as well as to reduce the chemical control in order to keep the environment free from any contamination with pesticides.