Effects of a parasitoid fly Compsilura concinnata, introduced as biological control, on a threatened nontarget silk moth Hemileuca maia at Otis Air National Guard Base, Cape Cod, Massachusetts, USA
Boettner G.H., Elkinton J.S. & Boettner C.J. (2000) Effects of a biological control introduction on three nontarget native species of Saturniid moths. Conservation Biology, 14,
BackgroundThe nontarget effects of a generalist parasitoid fly, Compsilura concinnata (Diptera: Tachinidae), introduced repeatedly to North America from 1906 to 1986 as a biological control agent against 13 pest species was experimentally examined, focusing primarily on two native, nontarget silk moths (Saturniidae), Hyalophora cecropia and Callosamia promethea in a Massachusetts forest (for a summary see: www.conservationevidence.com/ViewEntry.asp?ID=996). An additional small scale study, summarised here, of Hemileuca maia maia (a threatened native species) to investigate potential parasitism by C.concinnata was also undertaken.
ActionField-collected H.maia maia reared for C.concinnata: In 1998, a wild egg mass of H.maia maia, a state-listed (threatened) saturniid moth, was located on Otis Air National Guard Base, Cape Cod, Massachusetts (41˚39'N, 70˚34'W), northeast USA. Approximately 200 larvae hatched and fed gregariously on a bear oak Quercus ilicifolia. The larvae remained within a 20 m radius of the tree for the first three instars. A steep decline in numbers of the larval aggregation was observed during the third instar, so on 23 June 1998, 50 of the approximately 100 survivors were collected and reared in the laboratory to monitor for parasitoids.
It was found that C.concinnata parasitism was responsible for 36% (n = 50) mortality in the third instar Hemileuca maia maia larvae. Parasitism by this parasitoid fly may have also been implicated in the steep decline of this single larval aggregation observed in the field.
Thus, in terms of a management intervention to control insect pest species in forests, whilst C.concinnata has been effective at controlling several pest species, this introduced parasatoid fy may also be endangering native, nontarget insects, especially some silk moth species.
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