EVALUATION OF RESISTANCE OF ASIAN PEAR CULTIVARS TO PEAR PSYLLA (CACOPSYLLA PYRICOLA L.) UNDER TEHRAN ENVIRONMENTAL CONDITIONS

Pear psylla is one of the most important pests of pome and stone fruit trees. Pear trees were damaged more than any other hosts of this insect. Several researches in the biology field of this insect have been conducted during the past two decades. Therefore, assessment of Asian pear trees resistance, considering the value of this new product in the country, is required. For this purpose, this project was conducted in 2008 growing season in order to explore and monitor the resistance of some Asian pear (Pyrus serotina Rehd.) cultivars including ‘KS6’, ‘KS7’, ‘KS’8, ‘KS9’, ‘KS10’, ‘KS11’, ‘KS12’, ‘KS13’ and ‘KS14’ to pear psylla (Cacopsylla pyricola L.). Evaluation of insect resistance weredetermined based on the number of insects on leaves, the final product, the amount of fruit loss, leaf area, sugar content and leaf chlorophyll content. Among tested plant materials, ‘KS13’ with a few number of the pear psylla, ‘KS8’ and ‘KS14’ with lower fruit drop, were found to be moderately resistant to this pest of the antixenosis and tolerance types, respectively. Assessed correlation of sugar content and resistance, indicated that the cultivars with lower sugar content were resistant to the pear psylla. Leaf area did not show any significant correlation in respect to resistant to pear psylla.