Pear Psylla: Relationship of Early-Season Nymph Densities to Honeydew-Induced Fruit Damage on Two Pear Cultivars13

Abstract

The relationship of early-season densities of nymphs of Psylla pyricola Foerster to honeydew-induced fruit russet was measured on D’Anjou and Bosc pear cultivars in southern Oregon. Overall, fruit injury ratings based on percent downgrading caused by psylla honeydew indicated D’Anjou to be ca. fivefold more susceptible to damage induced by equivalent nymph densities than Bosc. An average nymph density of 1.0 per leaf resulted in ca. 2.5 and 17% downgrading on the Bosc and D’Anjou varieties, respectively. This difference was attributed to the nature of the pear cultivars, with damage being more apparent on the clear skinned D’Anjou compared with that on the normally russeted Bosc.