By pruning when beetle population and activities are at their lowest, chances of infestation are greatly minimized. Do not prune trees to minimize insect levels. By pruning, you are reducing the food making abilities of the tree, further weakening the specimen. Deep water, preferably using a drip emitter type system. This will ensure the tree has an adequate supply of water, especially during periods of drought.
Fertilizers often produce a flush of new growth the psyllids favor.
Riverside- click here Another UC Riverside article by Kathy Barton. Images Red Gum Lerp Psyllid images. These images were taken from an infested tree branch collected from the Veterans Parkway near Laurel Avenue in Manhattan Beach.