Experiments were performed to determine the role of the leafhopper Sophonia rufofascia (Kuoh & Kuoh) in damage observed on forest and watershed plants in the Hawaiian Islands. Laboratory manipulation of leafhopper populations on fiddlewood, Citharexylum spinosum L., caused interveinal chlorosis and vein browning on young fully expanded leaves similar to that observed on leafhopper infested plants seen in the field and necrosis on older leaves. Field studies with caged “uluhe” fern, Dicranopteris linearis (Burman), demonstrated that frond veins turned brown within 2 d of leafhopper feeding; and by 141 d after feeding, an average of 85% of the surface area of the fronds were necrotic compared with only 12% necrosis in untreated cages. Field trials with stump-cut firetree, Myrica faya Aiton, were performed to determine the effect of leafhopper feeding on new growth. Our studies showed that the new growth in exclusion cages had significantly greater stem length and diameter, a higher number of nodes, fewer damaged leaves, and almost twice as much leaf area compared with plants caged but with the sides left open to permit leafhopper access. Microscopic examination of sections through damaged areas of several leafhopper host plants showed vascular bundle abnormalities similar to those associated with hopperburn caused by potato leafhopper, Empoasca fabae (Harris), feeding on alfalfa. On Hawaiian tree fern, Cibotium splendens (Gaudichaud), oviposition into the midvein also disrupted vascular bundle integrity and often caused death of the distal portions of the pinnule.