■ Tachinids of Bertha Armyworm

The bertha armyworm, Mamestra configurata Walker, is a native North American species of noctuid moth ranging from Manitoba to British Columbia and south to Mexico (Crumb 1956). It was originally a feeder on native prairie plants but became a significant crop pest on the Canadian prairies in the 1920s, particularly on flax, sweet clover and alfalfa (King 1928). The bertha armyworm feeds on a wide variety of cultivated broadleaved plants but in recent decades has become of particular concern as a major pest of rapeseed and canola crops (Brassica napus L. and Brassica rapa L.) (Turnock 1984). Periodic outbreaks, most recently in 1994-1996, have caused significant economic losses to the agri-food industry (Mason et al. 1998). Information on the biology and pest status of the bertha armyworm can be found in papers by King (1928, 1929), Wylie and Bucher (1977), Turnock and Philip (1977), and Turnock (1984).

[image of a canola field]
Dr. Peter Mason inspects cages in a field of canola in Saskatchewan during an experiment on the parasitoids of bertha armyworm. (Photo by J.E. O'Hara.)

The parasitoids of bertha armyworm were virtually unknown until the severe outbreak of this pest in 1972. In that year studies were initiated at the Winnipeg research station of Agriculture Canada (now Agriculture and Agri-Food Canada) to investigate the control of insect pests on the oilseed rape crop in the prairie provinces of Canada. From these studies emerged a good understanding of the parasitoid complex attacking bertha armyworm during and between outbreaks (Wylie and coauthors, 1977-1979). Later work on bertha armyworm parasitoids concentrated mostly on individual species and their life histories and parasitoid/host interactions (eg. Arthur and Powell 1989, 1990; Arthur and Mason 1985, 1986; Turnock and Bilodeau 1992), and on new biological control possibilities (eg. Turnock 1984; Turnock and Carl 1995).

The primary purpose of these web pages is to provide provincial entomologists, biocontrol researchers and other non-specialists on the Tachinidae with the means to identify adult tachinids reared from bertha armyworm. To achieve this aim, these pages summarize what is known about the tachinid parasitoids of bertha armyworm and provides information on adult recognition, biology and distribution.