Spurge Biological Control in the Northeast

Heather Faubert & Richard Casagrande IntroductionCypress Spurge (Euphorbia cyparissias, L.) 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. It tends to form almost pure stands in pastures and other open sites, and is likely responsible for the displacement of rare native species. All plant parts 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 L.), 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. Of these 12 species, 6 species increased to populations large enough to collect and redistribute to other states. Starting in 1995 in the Northeast, 5 chrysomelid beetles and one gall midge were released to control both leafy spurge and cypress spurge.

MethodsMany or all 6 insect species were released at 3 cypress spurge infestations in Rhode Island, 2 leafy spurge infestations in New York, and one leafy spurge and 2 cypress spurge infestations in New Hampshire from 1995-1998. Insects were supplied by the USDA Biological Control Facility in Bozeman, MT. Release sites were monitored using sweep nets for insects and measuring areas of weed suppression. When insect populations increased sufficiently, insects were collected and redistributed to other locations.

Aphthona czwalinae (Weise) & A. lacertosa (Rosh.)

A. cyparissiae (Koch) &A. nigriscutisFoudras

A. flava Guill.

One year after release

Two years after release

Three years after release

ResultsAll 6 insect species were recovered in the 3 Northeastern states where they were released. Weed suppression was noted after one year in many locations. Significant weed reduction has occurred at release sites in Rhode Island and New York, but not in New Hampshire.

Release Site Aphthona spp.released Diameter of weed suppression

Rhode Island year following release

1 yr 2yr 3yr 4yrW. Alton Jones ‘96 500 A. flava 2m 5m 10m 50m

W. Alton Jones ‘95 500 A. czw/lac. none none none none

Watson #1 ‘95 500 A. czw/lac. none 2m 3m 3m

Watson #2 ‘96 1500 A. nigriscuys 2m 3m 15m 20m

Watson #3 ‘95 2000 A. cyparissiae 3m 10m 15m 35m

Watson #4 ‘96 750 A. flava none 6m 30m 50m

Aphthona spp. beetlesreceived and released.

Spurgia esulae galls readyfor release.

Cypress spurge

Insects releasedThe six insect species released in the Northeast include five chrysomelid beetles in the genus Aphthona and one cecidomyiid fly gall midge, Spurgia esulae Gagne.

ConclusionsAphthona flava appears to be the most effective biological control agent of cypress spurge in Rhode Island. In New York, Ahthona nigriscutis, A. lacertosa, and A. czwalinae seem to be the most effective on leafy spurge and cypress spurge. Insects have been collected and redistributed to other locations infested with cypress spurge or leafy spurge, including Hempstead Plains on Long Island, NY, a property of The Nature Conservancy. Some releases have not been effective, and it is unknown at this time what caused these to be unsuccessful.

Spurgia esulae Gagne

Typical release site

Aphthona flava defoliating cypress spurge at W. Alton Jones in Rhode Island.

Leafy spurge