ECOLOGICAL STUDIES ON THE OLIVE PSYLLID, EUPHYLLURA STRAMINEA LOGINOVA (HOMOPTERA: PSYLLOIDEA: APHALARIDAE) IN AL-ARISH, NORTH SINAI, EGYPT

The olive psyllid, Euphyllura straminea Log. is an economic impor­tant insect pest on olive trees in Egypt. The pest causes severe damage to the olive trees and decline the olive yield in Al-Arish, North Sinai. The present work was conducted for two successive years (1997/98 & 1998199) on a heavily infested olive orchard in Al-Arish. The seasonal abundance, the number of generations and effect of certain weather fac­tors on the population dynamics were studied. The obtained results showed that, The pest have five nymphal in-stars before maturity. The 1st instar nymphs appeared through Novem­ber or by early December and continued until late June and were abun­dant during March/April in both years. The 2nd instar nymphs appeared by mid- November or December and continued until late June and abun­dant in April in both years. The 3rd instar nymphs appeared from Decem­ber! January and continued until mid-July and abundant through April,' whereas the 4th instar nymphs appeared during January and continued until mid-August and abundant through April in both years. The 5th in-star nymphs appeared through January/February and continued until late August and more abundant through April/May in the two years. The adults occurred all the year round, abundant through April and have a re­productive dormancy in summer and autumn. Oviposition started in No­vember, eggs are deposited in the twig buds of olive shoots and the newly twigs of crowded branches, individually or in batches (2- 4 eggs). The pest had one generation a year on olive trees in Al-Arish, North Si­nai. The obtained results showed that, the tested weather factors were significant and negative correlation on the nymphal and adult popu­lations in both years, respectively. The exact effect of these factors on populations revealed that, night minimum temperatures (13.3-13.9°C) and maximum temperatures (25.3-26.3°C) were around optimal range for nymphal activity and within optimal range of the adult activity in the investigated years. The mean temperatures (19.3- 20.1 °C) were within optimal range of nymphal activity and around optimal range of adult ac­tivity in both years, respectively, whereas the relative humidity (67.6 69.4% R.H.) was above optimal range of nymphal and adult activities in both years, respectively. The combined effect of tested weather factors on nymphal popu­lation were highly significant in both years and the amounts of variability were 68.8% and 63.3% for both years, respectively. Whereas, its effect on adult population were highly significant during the 1st year and signif­icant in the 2nd year and the amount of variability were 71.4% and 53.2% for the studied years.