The browntail moth Euproctis chrysorrhoea, was introduced to North America near Boston from Europe in 1897. It became an important defoliator of many tree species throughout New England and was also a human health hazard due to severe skin rashes caused by urticating hairs from the larvae. Beginning around 1915, however, browntail populations receded gradually to coastal enclaves at the tip of Cape Cod and on islands in Casco Bay in Maine, where high densities have persisted ever since. Until now no studies have explained why it declined and why it persists in coastal enclaves. We present evidence that a major cause of the decline was the generalist tachinid parasitoid Compsilura concinnata, which was introduced to North America in 1906 to control gypsy moths. Analysis of historical data revealed high levels of parasitism of browntail moth by this species, but low levels in coastal areas. We confirm this pattern experimentally by creating artificial browntail populations at both inland and coastal locations on Cape Cod. Another introduced Tachinid, Carcelia laxifrons, causes high mortality to browntail larvae at coastal sites with rich vegetation and helps restict high browntail densities to dune habitats with sparse vegetation.
Species 1: Lepidoptera Lymantriidae Euproctis chrysorrhoea (browntail moth)
Species 2: Diptera Tachinidae Compsilura concinnata
Species 3: Diptera Tachinidae Carcelia laxifrons
Keywords: population dynamics, biological control
The ESA 2001 Annual Meeting - 2001: An Entomological Odyssey of ESA