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

: Two distinct seasonal forms were found for the common pistachio psylla, Agonoscena pistaciae, the most serious insect pest of cultivated pistachio trees, Pistacia vera in Iran. The two forms are different morphologically as well as biologically. The summer form is of light colour and readily mates and starts egg laying 1–2 days after emergence, whereas, the winter form is larger, generally darker and in reproductive diapause. The first form is observed under long photoperiod, while the second form is induced under a combination of short photoperiod and low temperature. The combination of long photoperiod and warm temperature enhanced post‐emergence ovarian development in the winter form, showing a close inverse correlation between pre‐oviposition period and increasing temperatures. Both forms of A. pistaciae are adapted to a wide temperature range of 20–30°C for reproduction, and the fecundity of psyllid adults of either summer‐ or winter forms was found to be very high under experimental conditions.