Cypress Spurge Biological Control in Rhode Island Heather Faubert & Richard Casagrande

Introduction Cypress Spurge (Euphorbia cyparissias) is an herbaceous perennial in the Euphorbiaceae family, introduced into North America as an ornamental plant in the 1860s. The plant escaped cultivation and became established on open ground, particularly in pastures. It tends to form almost pure stands in open sites and is likely to be responsible for the displacement of rare native species. All parts of the plant contain a white latex which is toxic to cows and horses when ingested. Cypress spurge is in the same subgenus, Esula, as leafy spurge (Euphorbia esula), another European introduction. Leafy spurge causes large economic losses annually in the Great Plains of the United States and Canada. Starting in 1961, USDA and Agriculture Canada began looking for natural enemies of leafy and cypress spurge in Europe. After years of host specificity testing, 12 insects were cleared for release in the United States. Cypress spurge Cows avoiding cypress spurge

Methods In 1994, Don and Heather Minto, from the Society for the Preservation of New England Antiquities (SPNEA) came to URI wanting to release biological control agents against a serious cypress spurge infestation at the Watson Farm in Jamestown, RI. After obtaining permits, we released six insect species on pastures and hayfields at Watson Farm and also at a hayfield at the Nettie Marie Jones Preserve at URI’s W. Alton Jones campus in West Greenwich. Aphthona spp. Beetles received and released. Spurgia esulae galls ready for release. Nettie Marie Jones Nature Preserve at W. Alton Jones campus

Insects The six insect species released in Rhode Island include five chrysomelid beetles in the genus Aphthona and one cecidomyiid fly gall midge, Spurgia esulae Gagne. Aphthona czwalinae (Weise)A. lacertosa (Rosh.)A. flava Guill. A. cyparissiae (Koch) & A. nigriscutisFoudras Spurgia esulae gall

Releases Aphthona species beetles were released in batches of beetles per release site. Release sites were monitored by sweeping for insects and measuring the diameter of suppressed cypress spurge for several years. Typical release site One year after release Two years after releaseThree years after release

Redistribution Two insect species, Aphthona flava and A. nigriscutis, succeeded in reducing cypress spurge at both Watson Farm and URI’s W. Alton Jones campus. In 2000, A. flava beetles were collected and redistributed to other Rhode Island pastures or farmland infested with cypress spurge. Huge population of A. flava at W. Alton Jones in The beetles defoliated the cypress spurge but did not feed on any other plants redistribution site in East Greenwich

Conclusions All six insect species released in Rhode Island became established. Also, there is no evidence of feeding by these insects on plants other than cypress spurge. Two of the six species, A. flava and A. nigriscutis, reproduced sufficiently for collection and redistribution. Approximately 60,000 A. flava beetles were collected from the Nettie Marie Jones Preserve at URI’s W. Alton Jones campus and released at 8 other pastures or hayfields throughout Rhode Island. We will continue to monitor all release sites for years to come. When additional farmland infested with cypress spurge is located, we will consider releasing these insects to control it.