Taxonomic name: Quadrastichus erythrinae Kim
Common names: erythrina gall wasp, erythrina gall wasp (EGW)
Organism type: insect
Unusual growths, caused by the Erythrina gall wasp (Quadrastichus erythrinae), on leaves and young shoots of coral trees (Erythrina spp). alerts to the presence of this emerging invasive species. Q. erythrinae measures a mere 1.5mm and may be spread easily via infected leaves from infected Erythrina specimens.
Female: Length 1.45–1.6 mm. Dark brown with yellow markings. Head yellow, except gena posteriorly brown. Antenna pale brown except scape posteriorly pale. Pronotum dark brown. The mid lobe of mesoscutum with a ‘‘V’’ shaped or inverted triangular dark brown area from anterior margin, the remainder yellow. Scapula yellow. Scutellum, axilla and dorsellum brown to light brown. Propodeum dark brown. Gaster brown. Fore and hind coxae brown. Mid coxa almost pale. Femora mostly brown to light brown. Specimens from Mauritius are generally darker than those from Singapore. Oviposter sheath not protruding, short in dorsal view (Kim Delvare and La Salle 2004).
Male. Length 1.0–1.15 mm. Pale coloration white to pale yellow as opposed to yellow in female. Head and antenna pale. Pronotum dark brown (but in lateral view, only upper half dark brown; lower half yellow to white). Scutellum and dorsellum pale brown. Axilla pale. Propodeum dark brown. Gaster in anterior half pale; remainder dark brown. Legs all pale. Antenna with 4 funicular segments; without the whorl of setae; F1 distinctly shorter than the other segments and slightly transverse; about 1.4 wider than long. Ventral plaque extending 0.4– 0.5 length of scape and placed in apical half. Gaster shorter than female. Genitalia elongate, with digitus about 0.4 length of the long, exserted aedagus (Kim Delvare and La Salle 2004).
natural forests, planted forests, urban areas
The Erythrina gall wasp infests Erythrina species, of which there are approximately 110 in tropical regions around the world. Erythrina are used as ornamentals, ‘living fences’, and nitrogen-fixing components of agroforestry systems.
Like other gall-forming eulophid wasps, the Erythrina gall wasp inserts its eggs inside young leaf and stem tissue. The wasp larvae, which develop within plant tissue, induce the formation of galls in the leaflets and petioles. As the infestation progresses, leaves curl and appear deformed while petioles and shoots become swollen. After feeding is complete, larvae pupate within the leaf and stem tissue. After pupation within the galls, adult wasps emerge after cutting exit holes through to the outside. Heavily galled leaves and stems result in a loss of growth and vigour. Severe infestations can cause defoliation and death of trees (Yang et al. 2004; Heu et al. 2006).
The Erythrina gall wasp infests Erythrina spp. of which there are approximately 110 mostly in tropical regions around the world. (Kim et al. 2004). Erythrina spp. are also known as coral trees and have a variety of functions in different locations. In Taiwan they are highly associated with farming and fishing activities (Yang et al. 2004). As indicated by its Latin name "erythros" meaning red, its obvious red flowers have been used as a sign of the arrival of spring and as a working calendar by tribal peoples (Yang et al. 2004). Specifically, the blooming of its showy red flowers serves as a signal to the coastal people to begin their ceremonies for catching flying fish, and for the Puyama people to plant sweet potatoes (Yang et al. 2004).
In Hawai'i the Erythrina gall wasp infests coral trees, Erythrina variegata, E. crista-galli and the native E. sandwicensis (Heu et al. 2006). E. sandwicensis, known as the wiliwili tree, is endemic to Hawai'i and a “keystone species in Hawai'i's lowland dry forest, one of the most endangered ecosystems in the world.” For a closer look at the threat posed by the Erythrina gall wasp to the native Hawai'i wiliwili, please see Wiliwili on Maui: threatened by the Erythrina gall wasp . Control of the spread of Erythrina gall wasp in Hawai'i was predicted to cost over $1 million in 2008 (Brannon, 2007).
The Erythrina gall wasp has caused approximately 95% mortality of Erythrina endemic to Hawai'i (E. sandwicensis and E. variegate ) over 2 years (Medeiros, 2008, personal communication, 28 Nov). The Erythrina gall wasp, although thought to be native to Africa (Gates & Delvare, 2008), has been identified as a threat to Erythrina trees in Latin America, Asia, Africa, and Oceania (including the Pacific) (Messing, 2008; Li et al. 2006).
Native range: Quadrastichus erythrinae is believed to be native to Africa.
Known introduced range: First collected in Florida on coral trees Erythrina variegata, now in Miami and Hawai'i; also known from Singapore, Mauritius and Reunion, Taiwan, Hong Kong, China, India, Thailand, Philippines, American Samoa, Guam and in the Amami Islands and Okinawa in Japan.
Introduction pathways to new locations
Ship: Boats carrying fallen infested leaves raise the risk of spreading Erythrina gall wasp (Quadrastichus erythrinae) (SPC 2006).
Local dispersal methods
Hikers' clothes/boots: Quadrastichus erythrinae may be transported on many items, including clothing and flowers (SPC 2006).
Wind dispersed: Quadrastichus erythrinae may be spread via the wind (SPC 2006).
Section being updated
A single female Erythrina gall wasp carries on average approximately 320 eggs (Yang et al. 2004).
Studies conducted by the Hawai'i Department of Agriculture (HDOA) on Erythrina gall wasp indicate a life cycle (egg to adult) of about 20 days. A one-day old female wasp contains about 60 mature eggs in its ovaries. The adult female wasp exhibited a preference for depositing eggs in very young terminal leaves and stems, but not mature leaves. Adult wasps not given any food survived less than 3 days (males - 2.5 days, females - 2.9 days) while those provided with honey lived longer (males - 10.3 days, females - 6.1 days). The sex ratio of emerging wasps in lab-infested plants was 7 males to 1 female (Heu et al. 2006).
Reviewed by: Gene-Sheng Tung Forest Protection Division, Taiwan Forestry Research Institute, Taipei, Taiwan, ROC
Compiled by: Major update underway: IUCN/SSC Invasive Species Specialist Group (ISSG)
Last Modified: Friday, 26 February 2010