The dynamics of the adult population of pear psylla, Cacopsylla pyri L. (Hom., Psyllidae) in the region of Magnesia (Greece)

Abstract

N u t i o na 1 A g ricul t u ral R e sea rc h Fo u nda t i on. Plan 1 P r o t cc I ion I n s t i t u t c o f Vo 1 o s . G rcece Abstract: During the years 1991 '92, the dynamics of the adult population of C'ucopsyllri p j r i L. mas 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 adult population of pear psylla was sampled in such a way that estimates can be directly related quantitatively with simultaneous estimates of the immature stages. During most of the year females were more abundant than males except during the period of high adult emergence and the period of diapause when sex ratio remained close to 1 : I .During the infestation period (February October) a large proportion of the females contained mature eggs except during the period of high emergence of new females when, briefly. the proportion of mature females in the total female population was low. The mean number of mature eggs per gravid female changed considerably during the same period (February-October). It was very high during late winter, spring and autumn and low during summer suggesting that ovarian development is depressed during summer. which may be due to high temperatures. Consequently, the daily rate of oviposition was high during spring and autumn and low during summer. During late winter (February-March) the daily rate of oviposition was low, although the females contained a high number of mature eggs suggesting that ovarian development and rate of oviposition are not equally affected by weather conditions. U S.

Role of Cacopsylla pyri in the epidemiology of pear decline in Spain

“…The sex ratio observed here in Spain, similar to that of other areas which have been studied (Priore, 1991;Lyoussoufi et al, 1994;Stratopoulou and Kapatos, 1995), indicates that there is a higher proportion of females than males. Almost all the year the sex ratio was less than 1:1, as the mortality rate of males is higher than that of females (Lyoussoufi et al, 1994;Stratopoulou and Kapatos, 1995). Only during the emergence of new pear psyllids and during winter, when the mortality rates for males and females are similar (Stratopoulou and Kapatos, 1995), was the sex ratio above 1:1.…”

“…Almost all the year the sex ratio was less than 1:1, as the mortality rate of males is higher than that of females (Lyoussoufi et al, 1994;Stratopoulou and Kapatos, 1995). Only during the emergence of new pear psyllids and during winter, when the mortality rates for males and females are similar (Stratopoulou and Kapatos, 1995), was the sex ratio above 1:1. Therefore, further detailed investigation is needed on C. pyri females to determine how they may be involved in the spread of the disease.…”

“…Since this pear psyllid is the most important one in Spain (Portillo et al, 1993), as in other Mediterranean countries (Lemoine, 1984;Stratopoulou and Kapatos, 1995;Carraro et al, 2001), C. pyri could also be the main vector of PD associated disease agent. The percentage of pear psylla carrying the PD phytoplasma showed a seasonal trend through the year, which coincides with the seasonal detection of PD phytoplasma in pear trees (Seemu¨ller et al, Presence of PD phytoplama was analysed using the nested-PCR procedure.…”

The seasonal forms and reproductive potential of the common pistachio psylla, Agonoscena pistaciae (Hem., Psylloidea)

“…Several investigations on population dynamics of the pear psylla demonstrated that, during the hot season, the reproductive rate declined significantly. In Cacopyslia pyri (Linnaeus) high temperature during the summer reduced the rate of ovarian development ( Stratopoulou and Kapatos , 1995). The present study suggests that the winter‐form psyllids have a good tolerance of high temperature because, under the extreme condition of constant 35°C, they could still reproduce well, similar to summer‐form individuals (327 and 349 eggs, respectively).…”

“…The existence of seasonal forms in insects has been reported and described for many insects, including aphids ( Dixon , 1973), pear psyllids ( Wong and Madsen , 1967; Mustafa and Hodgson , 1984; Stratopoulou and Kapatos , 1995; Civolani and Pasqualini , 2003; Soroker et al, 2003) and several lepidopterous species ( Nijhout 1997; Windig and Lammar , 1999; Nakasuji and Mizumoto , 2001; Šefrová , 2002; Greve et al, 2003). The life cycle of species of temperate origin usually includes some physiological mechanisms such as diapause, hibernation, seasonal variations or a behavioural response (e.g.…”