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ARS Home » Northeast Area » Newark, Delaware » Beneficial Insects Introduction Research Unit » Research » Publications at this Location » Publication #421008
Research Project: Biology, Ecology, Genetics, and Genomics of Introduced Species for Biological Control of Invasive and Other Insect Pests

Location: Beneficial Insects Introduction Research Unit

Title: Aprostocetus nitens (Hymenoptera: Eulophidae), an ectoparasitoid proposed for biological control of the destructive Erythrina gall wasp, Quadrastichus erythrinae, in Hawaii

Author
item RAMADAN, MOHSEN - State Of Hawaii
item YALEMAR, JULIANA - State Of Hawaii
item RUBINOFF, DANIEL - University Of Hawaii
item WRIGHT, MARK - University Of Hawaii
item BOKONON-GANTA, AIME - University Of Hawaii
item Wang, Xingeng

Submitted to: Insects
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/9/2025
Publication Date: 5/14/2025
Citation: Ramadan, M.M., Yalemar, J.A., Rubinoff, D., Wright, M.G., Bokonon-Ganta, A.H., Wang, X. 2025. Aprostocetus nitens (Hymenoptera: Eulophidae), an ectoparasitoid proposed for biological control of the destructive Erythrina gall wasp, Quadrastichus erythrinae, in Hawaii. Insects. https://doi.org/10.3390/insects16050519.
DOI: https://doi.org/10.3390/insects16050519

Interpretive Summary: The erythrina gall wasp (EGW) is native to Africa, but has invaded Hawaii, threatening native wiliwili trees in the Hawaiian Islands. Thousands of wiliwili trees used primarily for landscaping and windbreaks have been damaged by EGW throughout the state. To develop a biocontrol program for sustainable management of this invasive pest, natural enemies were surveyed in the pest’s native range in Africa, and two major natural enemies (parasitic wasps) were imported into Hawaii for evaluations. One of them has been released. Despite the successful establishment of the released natural enemy and its significant control of EGW, there was an opportunity to enhance biocontrol by adding the second parasitic wasp. In this study, we evaluated the host specificity of the second parasitic wasp and its compatibility with the established parasitic wasp. Results showed that the second natural enemy specifically targets EGW and is expected to complement the first natural enemy. Together, these two natural enemies will offer a promising solution to control EGW populations and protect wiliwili trees in Hawaii.

Technical Abstract: Aprostocetus nitens Prinsloo & Kelly (Hymenoptera: Eulophidae) was identified as one of four hymenopteran ectoparasitoids impacting three Quadrastichus spp. erythrina gall wasps (Q. bardus, Q. erythrinae, Q. gallicola) in the native eastern Africa. In Hawaii, the eurytomid wasp, Eurytoma erythrinae Gates & Delvare (Hymenoptera: Eurytomidae), was chosen to initiate a flourishing biocontrol program of Quadrastichus erythrinae Kim (Hymenoptera: Eulophidae) (EGW), formerly approved for statewide field-release in 2008. However, the parasitoid’s impact on the galled inflorescences and shoots was not adequate. Aprostocetus nitens was designated to solve this setback in the wiliwili trees, Erythrina sandwicensis Degener (Fabaceae), an ecologically and culturally important native Hawaiian tree species. To permit this parasitoid to be released for biocontrol program on the islands, choice and no-choice host specificity tests were conducted on seven non-target gall formers in the Hawaii Department of Agriculture, Insect Containment Facility. The parasitoid was extremely specific to EGW. The competition between this parasitoid and the established E. erythrinae was determined. Studies revealed that the release of a second parasitoid will complement the success of the eurytomid wasp for control of EGW and will improve the survival success of wiliwili. Unlike what was found in the native region, the Hawaiian laboratory colony is thelytokous produces only female offsprings. Life cycle took 20.1 ± 0.28 days under laboratory condition. Non-ovipositing female survived for 102.5 ± 2.9 days when fed honey and laid eggs for 25.1± 2.3 days with average fecundity of 156.7 ± 22.3 offspring/female. This value is 3.9-fold higher than offspring produced by Eurytoma erythrinae. Characteristics of A. nitens, host specificity, competition with E. erythrinae, and its tri-trophic food chain association with 15 Erythrina host plants and 5 gall wasp guilds in the native African regions were defined. Implications to reduce frequent galls on the native Erythrina plants and likely domination over E. erythrinae, are discussed.