Taxonomic name: Quadrastichus erythrinae Kim
Synonyms:
Common names: erythrina gall wasp, erythrina gall wasp (EGW)
Organism type: insect Unusual growths, caused by Erythrina gall wasp (Quadrastichus erythrinae), on leaves and young shoots of coral trees (Erythrina spp). alerts to the presence of this emerging invasive species. Quadrastichus erythrinae measures a mere 1.5mm and may be spread easily via infected leaves from infected Erythrina specimens. Description
Female: Length 1.45–1.6mm. Dark brown with yellow markings. The head is yellow, except gena posteriorly brown. The antenna are pale brown, except scape posteriorly pale. Pronotum is dark brown. The mid-lobe of mesoscutum is marked with a ‘‘V’’ shaped or inverted triangular dark brown area from anterior margin, the remainder yellow. Scapula is yellow. Scutellum, axilla and dorsellum are 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 1.0-1.15mm. Pale colouration 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)
Please see PaDIL (Pests and Diseases Image Library) Wasps: Erythrina gall wasp
Quadrastichus erythrinae Kim 2004 for high quality diagnostic and overview images. Occurs in:
natural forests, planted forests, urban areas Habitat description
Erythrina gall wasp Quadrastichus erythrinae infests Erythrina species, of which there are approximately 110 different species around the world (mostly in tropical regions). Erythrina are used as ornamentals, ‘living fences’, and nitrogen-fixing components of agroforestry systems. General impacts
Like other gall-forming eulophid wasps, eggs are inserted 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. According to Yang et al. (2004), severe infestations can cause defoliation and death of trees (Heu et al. 2006).
The Erythrina gall wasp infests Erythrina spp. of which there are approximately 110 around the world (mostly in tropical regions) (Kim Delvare and La Salle 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 signal to the coastal people to begin their ceremonies for catching flying fish, and for another people (the Puyama people) to plant sweet potatoes (Yang et al. 2004).
In Hai‘i, Erythrina variegata is also known as tigers claw, Indian coral and wiliwili-haole and is a common landscape tree (Heu et al. 2006). The Erythrina gall wasp infests the coral trees, Erythrina variegata, E. crista-galli and the native E. sandwicensis (Heu et al. 2006). A tall, columnar variety of E. variegata, also known as tropic coral, tall erythrina or tall wiliwili is used in Hawaii as a windbreak for soil and water conservation and for planting around farmsteads (Rotar et al. 1986, in Heu et al. 2006). For a closer look at the threat posed by the erythrina gall wasp to the native Hawaii wiliwili, please see Wiliwili on Maui: threatened by the Erythrina gall wasp. Geographical range
Native range: Erythrina gall wasp (Quadrastichus erythrinae) is believed to have originated in Africa but this remains unknown for certain (Erythrina Gall Wasp 2006).
Known introduced range: Countries in Asia and Australasia, including China and India (Erythrina Gall Wasp 2006). Introduction pathways to new locations
Ship: Boats carrying fallen infested leaves raise the risk of spreading Erythrina gall wasp (Quadrastichus erythrinae) (Erythrina Gall Wasp 2006).
Local dispersal methods
Hikers' clothes/boots: Quadrastichus erythrinae may be transported on many items, including clothing and flowers (Erythrina Gall Wasp 2006).
On animals (local): Quadrastichus erythrinae may be spread via the wind (Erythrina Gall Wasp 2006). Management information
If detected very early, it may be possible to eradicate an occurrence of Erythrina gall wasp (Quadrastichus erythrinae) on an island, but such efforts have so far been unsuccessful. Eliminating or treating infested Erythrina trees growing near ports could help reduce the likelihood of the wasps spreading (Erythrina Gall Wasp 2006).
Short-term control options are limited. Experiments with pruning have not been successful, but a systemic insecticide appears to be partly effective in protecting highly valued individual trees in Hawaii. It is hoped that eventually the wasp may be brought under control by one or more biological control agents from its native range. The Hawaii Department of Agriculture and the University of Hawaii are carrying out searches in Africa where the wasp is believed to have originated. If effective biological control agents are identified, then host-range testing to ensure their safety will have to be completed before they can be released to control the gall wasp. In the meantime it is important to avoid moving Erythrina leaves or stems from infested to uninfested places. The adult wasps are tiny (1–1.6mm) and extremely abundant around heavily infested trees (Erythrina Gall Wasp 2006). Reproduction
A single female Erythrina gall wasp (Quadrastichus erythrinae) carries on average approximately 320 eggs (Yang et al. 2004). Lifecycle stages
Studies conducted by the Hawaii Department of Agriculture (HDOA) on Erythrina gall wasp (Quadrastichus erythrinae) 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: IUCN/SSC Invasive Species Specialist Group (ISSG)
|
|
Last Modified: Wednesday, 26 April 2006
|
