THE DYNAMICS OF THE ADULT-POPULATION OF PEAR PSYLLA, CACOPSYLLA-PYRI L (HEM, PSYLLIDAE) IN THE REGION OF MAGNESIA (GREECE)

During the years 1991/92, the dynamics of the adult population of Caco psylla pyri L. was studied in Greece (region of Magnesia). At regular intervals during the year, estimates were obtained of the size of the population of males and females, percentage gravid females, sex ratio, number of eggs per gravid female and daily rate of oviposition. The a dult population of pear psylla was sampled in such a way that estimate s can be directly related quantitatively with simultaneous estimates o f the immature stages. During most of the year females were more abund ant than males except during the period of high adult emergence and th e period of diapause when sex ratio remained close to 1 : 1. During th e infestation period (February-October) a large proportion of the fema les contained mature eggs except during the period of high emergence o f new females when, briefly, the proportion of mature females in the t otal female population was low. The mean number of mature eggs per gra vid female changed considerably during the same period (February-Octob er). It was very high during late winter, spring and autumn and low du ring summer suggesting that ovarian development is depressed during su mmer, which may be due to high temperatures. Consequently, the daily r ate of oviposition was high during spring and autumn and low during su mmer. During late winter (February-March) the daily rate of ovipositio n was low, although the females contained a high number of mature eggs suggesting that ovarian development and rate of oviposition are not e qually affected by weather conditions.