Response of Tuscan Pyrus communis L. cultivars to pear psylla artificial infestation

The development of Cacopsylla pyri was observed on 24 European pear cultivars regarded as native to Tuscany. 'Williams', known to be sensitive and 'NY 10355' ( hybrid P. ussuriensis x P. communis), known to be resistant, were used as control. The study was conducted in a semi-confined environment (screen house), provided laterally with a shading net. Pear trees (6 replicates per cultivar) were artificially infested introducing 5 females and 2 males pear psylla on one actively growing shoot per each tree closed by an insect-proof sleeve cage. The possible host resistance was investigated by evaluating insect oviposition and antibiosis reaction. Nymphal survival and adult emergence of the psylla populations were recorded over 40-day period on each cultivar. Ovipositional response showed that all pear cultivars were attractive, however, four levels of egg-laying during a 2-day oviposition could be distinguished (P<0.01). 'Assuntina', 'Etrusca', and 'NY 10355' received the lowest number of eggs (<56), while 'Pinzuta' and 'Coscia' were the most preferred cultivars for oviposition (approximate to 230). Great variations among pear psylla development were observed in antibiosis. No adults developed on 'NY 10355'. Pear cultivars that showed higher antibiosis effect ('Allora' and 'San Giovanni') did not always display non preference for oviposition. A growth delay and late development of the nymphs was highlighted in 'Moscatellina', with the almost total presence of nymphs and the emergence of a few number of adults at the end of the trial.