The Umbonia Spinosa, thorn bug, is an occasional pest of ornamentals and fruit trees in southern Florida. During heavy infestations, nymphs and adults form dense clusters around the twigs, branches and even small tree trunks. Some hosts that have been severely damaged include Hibiscus sp., powder-puff (Calliandra spp.), woman’s tongue tree (Albizzia lebbek), and Acacia spp. Young trees of jacaranda (Jacaranda acutifolia) and royal poinciana (Delonix regia) with a diameter of 1.5 to 2 inches have been killed by thorn bugs in the Tampa area. The trunks were so heavily infested that is was difficult to place a finger anywhere on the trunk without touching a specimen.
The thorn bug causes damage by piercing the plant tissue and sucking the sap and by making cuts in the plant for oviposition. Butcher (1953) reported that certain trees, especially some cassias, suffered considerable loss of foliage, and that pithecellobiums (Pithecellobium spp.) suffered general and extensive terminal twig death. He also mentioned that thorn bug honeydew secretions and accompanying sooty mold development caused a nuisance to home owners. Kuitert (1958) noted that heavy accumulations of honeydew sometimes occurred on parked automobiles.