Phenology of population of immature stages of Pear Psylla, Cacopsylla pyri, in the region of Magnesia (Greece).

The phenology of the population of immature stages of pear psylla, Cacopsylla pyri (L.), was studied in Greece (region of Magnesia), during the period 1988-1991 and it was found to follow a basic pattern. Pear psylla produces 5-6 generations per year. The first generation develops during the period February-middle April and it is quite discrete. Three overlapping generations are developed during the period from middle April until middle August but the amount of overlapping varies from year to year. From middle August until the end of the season pear psylla produces 1-2 generations, i.e. only a part of the fifth generation completes the sixth one. Population density is generally low during the first generation but during May-June reaches very high levels. During summer, strong environmental pressure, suppresses the population of pear psylla to low levels but it recovers again during September-October.