Host Range, Release, and Establishment of Sericothrips staphylinus Haliday (Thysanoptera: Thripidae) as a Biological Control Agent for Gorse, Ulex europaeus L. (Fabaceae), in New Zealand and Hawaii

This paper presents the results of tests to determine the host range of Sericothrips staphylinus Haliday (Thysanoptera: Thripidae), an agent selected for control of Ulex europaeus (Fabaceae). It also describes the biology of the thrips and its release and establishment in New Zealand and Hawaii. Eighty-three plant species were tested. Research was conducted in several institutions by use of five testing methods. Adult thrips survived for up to 15 days without food or longer on nonhost plants (causing small feeding scars). Female thrips laid eggs on several species of the Fabaceae other than U. europaeus, but with one exception, larvae died. Chamaecytisus palmensis (Christ) Bisby et K. Nichols supported the development of one adult in nine laboratory tests. Thrips produced adults on this plant in field cage tests, but in small numbers compared to controls. S. staphylinus appears to be narrowly oligophagous, but might establish on C. palmensis. At 19°C, females laid 1 egg per day on seedlings, for up to 8 weeks. Lifetime fecundity averaged 76 eggs per female. Development from egg to adult took 42 days. Thrips originating from the United Kingdom were released at 129 sites in New Zealand and have established at 59% of sites to date. Thrips originating from the United Kingdom, Portugal, and France were released in Hawaii, and all established. Thrips have caused heavy foliar damage at some field sites, and growth of the target weed has been significantly reduced in laboratory experiments. However, the impact of S. staphylinus on the gorse problem in New Zealand and Hawaii remains to be seen.