Agricultural and Forest Entomology (2017), DOI: 10.1111/afe.12214 Is there reproductive diapause in the winterform of pear psylla Cacopsyla bidens? Reut Madar ∗† , Yalta Zamir ∗† , Anna Litovsky ∗ and Victoria Soroker ∗ ∗ Department of Entomology, Institute of Plant Protection, Agricultural Research Organization, The Volcani Center, 68 HaMaccabim Road, Rishon LeZion, PO Box 15159, 7505101, Israel and † Institute of Agroecology and Plant Health, Robert H. Smith Faculty of Agriculture, Food and Environment, Hebrew University of Jerusalem, PO Box 12, Rehovot, 76100, Israel Abstract 1 Seasonal changes in reproductive state were investigated in the pear psylla Cacopsylla bidens (Šulc), with a particular emphasis on the evaluation of reproductive diapause during autumn and winter. 2 Changes in reproductive status were observed in both seasons in populations living at four altitudes: 70, 300, 700 and 730 m. Winterform psylla females exhibited a period of slow ovarian development and a low mating rate. The onset, duration and extent of this period varied among the four sites but terminated synchronously, around December 20th. These changes were consistent within the same population over 3 years. 3 Laboratory and field data suggested that winterform female C. bidens maintain some characteristics of reproductive diapause. By manipulating photoperiod and temperature during psylla development, we showed a major role for photoperiod in the induction of a reproductive diapause-like state. However, as observed under natural conditions, the timing of the decrease in ovarian development and mating was highly dependent on the decrease in temperature. 4 The fact that the initiation of reproductive activity was synchronous and highly predictable is very significant for the design of phenologically based management for this pest. Keywords Homoptera, ovarian development, photoperiod, polymorphism. Introduction Seven species of pear-feeding psyllids (Homoptera: Psyllidae) in the genus Cacopsylla occur in Europe and North America (Burckhardt & Hodkinson, 1986). Several of these species are important pests of pears (Pyrus communis), including Cacop- sylla bidens (Šulc) in Europe and the Mediterranean region. The European and North American pear psyllid Cacopsylla pyricola and the European Cacopsylla pyri L. both display seasonal morphological and physiological dimorphism. The summer- forms are small and light-coloured, whereas the winterforms are larger and dark (Oldfield, 1970). Cacopsylla pyricola and C. pyri exhibit reproductive diapause during the winter months, as characterized by a lack of mating and immature ovaries (Krysan & Higbee, 1990; Kapatos & Stratopoulou, 1996). These seasonal changes fit well with the phenology of their deciduous host plant. Much less information exists on the phenology and physiology Correspondence: Victoria Soroker. Tel.: +972 3 9683832; fax: +97 2396 83906; e-mail: sorokerv@agri.gov.il of C. bidens. In Israel, it is multivoltine, with approximately nine generations per year (Shaltiel-Harpaz et al., 2014), pre- senting a serious challenge for its control. It shows seasonal polymorphism that is expressed in body and wing size, as well as colour (Swirski, 1954; Soroker et al., 2003). The transition from the small and light-coloured summerform to the large and dark-coloured winterform appears to be gradual: in autumn, psylla individuals are of intermediate size and colour (Soroker et al., 2003). The winterforms appear to be produced in response to the short photoperiods and lower temperatures experienced by the nymphs (Soroker et al., 2013). However, whether reproduc- tive diapause is expressed in this species under the mild winter conditions of the southern Mediterranean region is not clear. The present study aimed to evaluate the reproductive state of C. bidens females, particularly during the autumn–winter period. To assess the relative contributions of photoperiod and temperature to psylla reproduction, we examined females from several altitudes. We further compared females from the same altitude over a number of years, as well as females reared in the laboratory under different combinations of temperature and photoperiod. © 2017 Agricultural Research Organization The Volcani Center