Threshold Moisture Status of Apple Trees During the Development of Scolytus nitidus

Among hosts of Scolylus nitidus Schedl recorded during present investigations, apple was the most attractive host compared to almond, cherry, apricot, plum, peach, pear and walnut. The beetles preferred to attack apple trees having branches of 4-6 cm in diameter with 4-6 mm thick bark at a height of 406 feet from ground level. Three indices of habitat influences in relation to beetle development were monitored. Moisture content of apple trees in the outer bark, inner bark and secondary. The moisture content of control trees was used as the threshold moisture at the time of beetle attack and was estimated to be 50.7%, 52.1% and 33.1% for outer bark, inner bark and secondary xylem, respectively.