Quadrastichus erythrinae
Erythrina gall wasp - Quadrastichus erythrinae Kim
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Erythrina gall wasp
Like other dryland plants in Hawai'i, the wiliwili tree (Erythrina sandwicensis) faces numerous threats, including a non-native seed weevil, Specularius impressithorax (Hurley, 2005), fire - fueled in part by invading fountain grass, and feral ungulates (LaRosa, pers. comm., 2005). The latest threat is the erythrina gall wasp, which was discovered on Oahu in April 2005. Over the summer, the gall wasp was discovered damaging trees on Kaua'i, Maui, and the Kona side of the island of Hawai'i (Hurley, 2005). Most recently, it has been documented on Molokai as well (Monson, 2005). Currently (mid-September, 2005), twenty-four species in the genus Erythrina (of which one is native to Hawai`i) have been documented as hosts (Fulton, pers. comm., 2005).
Concern focuses on the likely impacts to the native wiliwili, a tree of great societal, cultural (Hurley, 2005) and ecological importance. The state's largest intact stands of native wiliwili are on Maui, where the wiliwili is the keystone species of the low dryland forest (Madeiros, pers. comm., 2005). By September 2005, widespread infestations were observed and the efforts to contain the gall wasp by pruning out infestations had not succeeded (Monson, 2005).
In an effort to conserve the wiliwili trees, many scientists and concerned citizens have begun a program to collect seeds for preservation - although there are numerous questions on how to proceed. Protecting the full range of genetic diversity is the main goal, however, it is unknown whether diversity varies from island to island or even among various habitat types on each island. Experts at the USDA National Center for Genetic Resources Preservation (formerly National Seed Storage Laboratory) in Ft. Collins, Colorado have offered advice and seed preservation and storage assistance (Ellis, pers. comm., 2005).
Citizens and scientists are trying to protect trees through injection or soil drench with systemic insecticides. The efficacy of the insecticide over the long term is not yet known; in Taiwan, chemical controls have not proven effective. Other scientists are hoping to explore possible biological control agents (Wright, pers. comm., 2005).
A scientist first identified the erythrina gall wasp in 2004 when examining specimens collected from Singapore and the Mauritius and Reunion islands (Hurley, 2005). The gall wasp has since been found in Taiwan, India, Hawaii, Hong Kong, China, and the Philippines. The wasp is believed to be African in origin, based on the presence of closely related species (La Salle, pers. comm., 2005).
If the erythrina gall wasp spreads further, it might also threaten Erythrina in the mainland United States or in tropical America. There are two native Erythrina species in the southern U.S.: Erythrina flabelliformis is found in the Sonoran desert and E. herbacea ranges from Texas to South Florida and North Carolina. Seventy species could also be impacted in the American tropics, such as native E. corallodendron, E. corallodendron var. connata, and E. eggersii (Loope, pers. comm., 2005).
Sources
Ellis, David. 2005. Plant physiologist, U.S. Department of Agriculture, Agricultural Research Service. Personal communication. David.ellis(at)ars.usda.gov.
Fulton, Will. 2005. Horticulturalist, National Tropical Botanical Gardens - http://ntbg.org. Personal communication. wfulton(at)ntbg.org.
Hurley, T. 2005. Tiny wasp may kill off native trees. Honolulu Advertiser Newspaper. Thurley(at)honoluluadvertiser.com.
LaRosa, Anne Marie. 2005. Forest Health Coordinator, Institute of Pacific Islands Forestry, U.S. Department of Agriculture Forest Service. Personal communication. alarosa(at)fs.fed.us.
La Salle, John. 2005. Head of the National Australian Insect Collection, CSIRO Entomology. Personal communication. John.lasalle(at)csiro.au.
Loope, Lloyd. 2005. Research Scientist, U.S. Geological Survey. Personal communication. Lloyd_loope(at)usgs.gov.
Medeiros, Arthur C. 2005. Research Biologist, U.S. Geological Survey. Personal communication. acm(at)aloha.net.
Monson, V. 2005. Efforts to control erythrina gall wasps fail. The Maui News. vmonson(at)mauinews.com.
Wright, Mark. 2005. Assistant Professor and Extension Specialist, University of Hawaii. Personal communication. markwrig(at)hawaii.edu.
