Leaf hoppers are sap-sucking insects that attack a wide range of plants. One or two won't cause significant damage, but lots of them can cause leaf yellowing and overall weakening of the plant.
Leaf hoppers are yellowish in colour and around 2-3mm long. As their name suggests, they (the adults) will jump off if their plant home is disturbed. The immature nymphs are creamy white and crawl. Both nymphs and adults feed on the sap of plants.
Colonies on the underside of leaves will have up to 3 generations present at any 1 time. Leaves will become gradually paler with white surface mottling.
The rhododendron leaf hopper is responsible for spreading the fungal disease bud blast, which kills the flower buds.
Spray with a natural-based insecticide. Pyrethrin (a natural plant extract) based insecticides will control leaf hoppers and other plant pests.
Spray with a general insecticide. Most broad spectrum insecticides will control leaf hoppers. They kill very quickly on contact and also have a residual effect which lasts for a few weeks.