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- Title
Reproductive Parameters and Host Specificity of Eurytoma erythrinae (Hymenoptera: Eurytomidae), a Biological Control Agent of the Erythrina Gall Wasp, Quadrastichus erythrinae (Hymenoptera: Eulophidae).
- Authors
Nagamine, Walter T.; Yalemar, Juliana A.; Wright, Mark G.; Ramadan, Mohsen M.
- Abstract
Simple Summary: The erythrina gall wasp, Quadrastichus erythrinae (Hymenoptera: Eulophidae), invaded Hawaii in April 2005 and rapidly dispersed throughout all the Hawaiian Islands in less than a year. Severe infestations devastated native and introduced trees of the genus Erythrina (Fabaceae), destroying thousands in the Western Pacific and Hawaii. Recently, this wasp has become a serious pest of Erythrina species around the world, including mainland USA, Mexico, and the Neotropical region. Expensive maintenance and chemical control measures have failed to contain this gall wasp and biocontrol was thought to be the only long-term solution. Exploratory trips in Tropical East Africa, South and West Africa, and Madagascar were undertaken during December 2005–June 2006 to determine the origin of this pest and survey its associated parasitoids as potential biocontrol agents. Tanzania was selected as a focal point of exploration because of the number of Erythrina species listed to be endemic to that country, more than anywhere else in Africa. Three hymenopteran ectoparasitoids were found in association with the galls, a eurytomid (Eurytoma sp.) and two eulophids (Aprostocetus spp.), whose larvae develop within the galls on immature stages of the gall former. Parasitoids from the Tanzanian and South African collections were amenable for insectary rearing on EGW from Hawaii. Host specificity and biology studies were conducted on the dominant parasitoid, Eurytoma erythrinae, in a containment facility in Hawaii. The parasitoid was found to be specific to EGW and was approved for release with good results in reducing the impact of the pest, saving the native Erythrina trees in Hawaii. We report on reproductive performance, rearing biology, host specificity testing, and the implication for biocontrol elsewhere with EGW problems. Eurytoma erythrinae Gates & Delvare (Hymenoptera: Eurytomidae) is an important biological control agent of the erythrina gall wasp (EGW), Quadrastichus erythrinae Kim (Hymenoptera: Eulophidae), an invasive species likely originating in eastern Africa that is a threat to Erythrina trees in Hawaii and worldwide. Thousands of Erythrina trees in Hawaii have succumbed to EGW since 2005 and died within a few years of infestation. The endemic wiliwili tree, Erythrina sandwicensis, an important component of Hawaii's dry forests and one of few deciduous native trees, were severely impacted by this wasp. Early during the invasion by EGW it became evident that the endemic species may be driven to extinction, and exploration programs for natural enemies of the EGW started in December 2005. East Africa was selected as the starting point for natural enemy exploration owing to high native Erythina species richness. Several gall formers were found in Tanzania and a putative color variant type of Q. erythrinae was detected in association with three ectoparasitoids. During January 2006, the dominant parasitoid of this gall former was introduced to Hawaii and described as the new species, E. erythrinae. It was found in Ghana and South Africa attacking other gall wasp species on Erythrina. Eurytoma erythrinae was a voracious ectoparasitoid feeding as a predator on 1–5 adjacent EGW immatures to complete its development. Host specificity studies that included seven nontarget gall-forming species showed no evidence of attraction or parasitism by this parasitoid. Mean ± SEM longevity of host-deprived females (40.4 ± 2.2 days) was significantly higher than males (20.5 ± 1.1 days). Host feeding enhanced longevity of ovipositing females (51.3 ± 1.5 days). Female E. erythrinae is synovigenic, with high egg-maturation rate. Peak fecundity (105–239 offspring/female), host feeding biology, short life cycle (18.4 ± 0.1 days), and synchronization with the host were additional desirable attributes of this species. The parasitoid was approved for field release in Hawaii in November 2008. A total of 3998 wasps were distributed on six Hawaiian Islands, with establishment in less than a year. Impacts on high density infestations of EGW were sufficient to prevent tree deaths. Limited rates of parasitism on low-density galled leaves, flowers, and seedpods necessitated the consideration for releasing a second parasitoid, Aprostocetus nitens Prinsloo & Kelly (Hymenoptera: Eulophidae). We report on the reproductive characteristics and host specificity of E. erythinae that could be of importance for classical biocontrol programs in areas with an EGW problem.
- Subjects
HAWAII; GALL wasps; BIOLOGICAL pest control agents; HYMENOPTERA; EULOPHIDAE; GALL midges; HOST specificity (Biology); BROOD parasitism
- Publication
Insects (2075-4450), 2023, Vol 14, Issue 12, p923
- ISSN
2075-4450
- Publication type
Article
- DOI
10.3390/insects14120923