psylla

The name of the plant louse that infests pear trees is the pear-tree psylla.

The psylla, while irregular in its outbreaks, is most damaging and hard to control when it appears.

Kieffer and related hybrids are somewhat immune to San Jose scale, but are very susceptible to psylla.

Other pests, as psylla, the scab-fungus, and codling-moth beset the pear and make profits uncertain.

The psylla is a minute, sucking insect, wingless in its immature stages, but winged and very active as an adult.