BIONOMICS OF THE COMMON PISTACHIO PSYLLA, AGONOSCENA PISTACIAE, IN IRAN

Abstract

The common pistachio psylla, Agonoscena pistaciae Burckhardt and Lauterer (Hemiptera: Psylloidea), is the key pest of cultivated pistachio trees, Pistacia vera (L.), and is distributed throughout all the pistachio-producing regions in Iran. This study focused on various features of the pest and was carried out both in the laboratory and the field under natural conditions. It was found that the common pistachio psylla has two seasonal forms. Clear morphological and physiological differences between the adult psyllid morphs were observed. However, both temperature and photoperiod strongly influenced diapause induction and termination in this insect. The optimum constant temperature for development was 30°C, however, the psyllid nymphs developed quickly, between 25 and 32.5°C. Both summer- and winter-forms of A. pistaciae are adapted to a wide temperature range for reproduction. Egg laying only started after mating and oviposition continued until death. This study indicated the important role of male psyllids in progeny production in the common pistachio psylla. In addition, several life-cycle parameters including thermal thresholds and constant, actual fecundity and intrinsic rate of natural increase for the psyllid were determined. In the Kerman province, the winter-form adult psyllids first emerged in early October and continued throughout the autumn until early December, emigrating towards the overwintering sites. Afterwards, the winter-forms appear in the pistachio orchards in the late winter and early spring and attack pistachio trees, feed on swollen buds, young leaves and shoots and establish the summer-form generation. Most first generation adult psyllids appeared around early May, when the founders’ winter-form psyllid was still active on the pistachio trees. The pest population rapidly increases from early spring to late autumn. However, the presence of high population densities of psyllid nymphs and adults causes significant economic losses, particularly from the late spring to nearly the end of summer. The control of this pest relies almost exclusively on pesticides. However, the parasitoid wasp, Psyllaephagus pistaciae Ferriere, and the predatory ladybird, Oenopia conglobata (Linnaeaus), are the major biocontrol agents for this insect. The effects of other potential predators such as lacewing, ladybirds, mites, spiders and anthocorid bugs have not yet been fully investigated, but it is thought that these natural enemies all play a significant role in the control of the common pistachio psylla, particularly in the spring and autumn.