Answer: In a nutshell, what you've heard is true. Here's a little background information on psyllids in general:
Psyllids resemble miniature cicadas and are sometimes called jumping plantlice. Over 100 species occur on both native and introduced landscape plants in the United States, but each kind of psyllid feeds on only one plant species or closely related groups of plants. Most psyllids native to the United States are relatively uncommon and rarely become pests. Most pest psyllids in California are exotic species inadvertently introduced from other countries.
Adult females lay eggs that hatch and develop through about five wingless, immature nymphal stages before becoming winged adults. Most pest psyllids in California occur on evergreen plants in mild-climate areas where all life stages may be found year-round. Psyllids become abundant in spring when temperatures warm and host plants produce new growth flushes. One psyllid generation requires only a few weeks during warm weather to complete development from egg to egg. High temperatures may reduce populations of some species.
Eugenia psyllid occurs primarily on Australian brush cherry or eugenia (Syzygium paniculatum). Adults are mostly dark brown with a white band around the abdomen. Their tiny golden eggs are laid primarily along the edges of young leaves, causing infested leaf margins to glisten in the sun. Nymphs are yellowish with orange-red eyes. Recently hatched first-instar nymphs (called crawlers) settle on new growth and each forms a feeding pit. Settled nymphs resemble a soft scale insect and appear flat when viewed from the lower leaf surface. The upper surface of infested foliage reddens and distorts above these pits. Eugenia psyllid has about three to about five generations a year, depending on temperature and host plant suitability. High populations in California are limited to counties near the coast.
Eugenia psyllid is partially controlled by an introduced Tamarixia species of parasitic wasps. However, especially in cooler areas near the California coast, parasite populations often do not increase quickly enough in spring to provide satisfactory control. Regular shearing of new growth provides substantial control by removing psyllid eggs and nymphs. Well-timed pruning in combination with parasite conservation can be especially effective in managing psyllids infesting eugenia plantings.
Hope this sheds some light on the problem!
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