They undoubtedly will move into Africa. Nymphs cause the primary damage by sucking sap from young foliage. Leaflets turn yellow, curl, and wilt. The deposition of honeydew encourages the growth of sooty molds. Complete defoliation of terminal shoots can occur under heavy psyllid infestation.
Trees usually survive unless they are subject to other severe stresses, such as a drought.
Damage usually has been the most severe just after the psyllids invade an area. Trees were almost bare in Hawaii during the first year of attack, which coincided with a severe drought. Defoliation has occurred rather cyclically since then. When leaf growth slowed in the dry season, the already high psyllid populations caused the most severe damage. Psyllid populations dropped to very low levels at the end of the dry period due to the lack growing young shoots.