Polyploidy as a Potential Erythrina Gall Wasp Management Strategy

The erythrina gall wasp (EGW; Quadrastichus erythrinae Kim) was first collected in Hawaii in 2005 on Erythrina variegata L., a then popular landscape species. It quickly spread to all islands causing severe damage to the native Erythrina sandwicensis Degener as well as most introduced species. E. variegata ‘Tropic Coral’, a fastigiate form was widely used as a windbreak for crop protection and soil and water conservation. However, today it is nowhere to be found. Galls on leaves, petioles and stems are induced by the larvae of the tiny EGW. Larvae develop within plant tissues, causing the formation of galls on leaves, petioles and stems. Leaves curl and become massively deformed while petioles and stems become swollen. Heavy infestations cause defoliation and death of trees. Thousands of trees have been killed by this pest. Polyploid individuals of E. variegata show a high level of tolerance to the EGW, while in the same plot diploid individuals are destroyed or nearly destroyed. The induction of polyploidy in EGW-susceptible Erythrina variegata may be a strategy to return this species and its cultivar ‘Tropic Coral’ to cultivation in Hawaii and other areas where this pest is a problem.