Biological Control of Pests in Forests of Eastern United States

 

 

 BROWNTAIL MOTH

(Euproctis chrysorrhoea [L.])

Joe Elkinton and Jeff Boettner, University of Massachusetts, Amherst elk@ent.umass.edu

Range in North America

Browntail moth (BTM), Euproctis chrysorrhoea, is a European lymantriid moth that invaded North America near Boston, Massachusetts in about 1897. By 1914 it had spread north to New Brunswick, Canada, and west to Vermont and the Connecticut River Valley in Massachusetts and Connecticut. This invaded range subsequently retracted and the pest is currently highly restricted to a few tiny coastal enclaves in Massachusetts and Maine (Elkinton et al., 2006).

Damage

Initially the damage from browntail moth was similar to that from gypsy moth (Lymantria disapar [L.]), being widespread defoliation of deciduous forest and fruit trees.  Currently, because of its restricted range, the insect is only found on a few shrubs, especially beach plum  (Prunus maritima), native to the coastal dune community.  However, in addition to being an important defoliator, this moth was also a serious public health problem because the larvae's urticating hairs caused severe skin rashes in people (Blair, 1979) and even some deaths (Schaefer, 1974).

Resident Natural Enemies

Apart from introduced species, only generalist natural enemies are associated with browntail moth in North America.

Biological Control Attempts Against the Pest

Several parasitoids were introduced for control of both the gypsy moth and the browntail moth, especially three tachinid flies: Townsendiellomyia nidicola and Carcelia laxifrons, both BTM specialists, and Compsilura concinnata, a polyphagous species (Howard and Fiske, 1911).  By the 1920s, the range of browntail moth was retracting toward the coast and little further research was conducted on the species, except that of Schaefer (1974)

Up to the Minute Status

Why browntail moth populations collapsed was not investigated at the time, due to a preoccupation with the expanding and damaging populations of gypsy moth.  In 2000 and 2001, Elkinton and associates conducted transplant experiments that showed that at inland habitats (typical of where the pest had disappeared) the tachinid Compsilura concinnata caused high levels of mortality (30-40%) and that artificially established browntail moth populations in these areas failed to persist. In contrast, in coastal scrub areas where browntail moth has persisted, C. concinnata parasitism was much lower (<10%) and tranplanted populations survived (Elkinton et al., 2006).  Based on these outcomes and other data, it is now certain that the introduction of C. concinnata was the reason for the control of browntail moth.

Photos

Top left: larvae of browntail moth (photo credit: Andrea Battisti, Forestryimage.org)

References Cited

Blair, C. P. 1979. The browntail moth, its caterpillar and their rash. Clinical and Experimental Dermatology 4: 215-222.

Howard, L. O. and W. F. Fiske. 1911. The importation into the United States of the parasites of the gypsy moth and the browntail moth. Entomological Bulletin No. 1911. United States Department of Agriculture, Washington, D.C.

Elkinton, J. S., D. Parry, and G. H. Boettner. 2006. Implicating an introduced generalist parasitoid in the invasive browntail moth's enigmatic demise. Ecology 87: 2664-2672.

Schaefer, P. W. 1974. Population ecology of the browntail moth, Euproctis chrysorrhoea (Lepidoptera: Lymantriidae). Dissertation, University of Maine, Ornono, Maine, USA