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Background
Table 73
D. Testing of Parasitoids
I.W. VARTY
D. Testing of parasitoids 267
The two strategies for biological control of the spruce budwonn, CJwristoneura fwniferatUl
(Clem.), by parasitoids are the introduction of exotic species and the manipulation of
native ones. Most entomologists agree that the best prospects for introduction are those
species that parasitize Choristoneura spp. (or near relatives) in spruce (Picea spp.) and fir
(Abies spp.) forests in similar climatic zones abroad. The problem is to be ready for
opportunities in those few years when pest outbreaks overseas permit sizeable collections
of candidate parasitoids. The manipulation of native parasitoids offers two other avenues
for action: inundative release of laboratory-reared stock, and management of forest
habitats to favour the dynamics of parasitoid response to available hosts.
Efforts to establish exotic parasitoids in spruce budworm populations of eastern
Canada have not succeeded. In 1944-53, large numbers of four species (two tachinids,
one sarcophagid, and one ichneumonoid) from unidentified western spruce budworms
(British Columbia) were released at various sites from Manitoba to Newfoundland. In
1948-56, 12 ichneumonoid species from European hosts, especially Choristoneura
murinana (Hb.) (France, Germany, Czechoslovakia), were released in small numbers
in northwestern Ontario and Quebec. No evidence of the establishment of any introduced
species has been produced (McGugan & CoppeI1962), and there were no explanations
of the causes of failure. Interest in further introductions was inhibited by these failures
and by lack of sources of parasitoids abroad. However, during the 1960s unsuccessful
efforts were made to obtain three ichneumonoids specific to C. murinana (Miller &
Angus 1971).
Interest was renewed when an outbreak of Choristoneura diversana (Hb.) on Japanese
(todo) fir (Abies firma Sieb & Zucc.) in Hokkaido, Japan, occurred in the late 1960s.
Collaboration among four institutes (Hokkaido Forest Experimental Station, Maritimes
Forest Research Centre, Commonwealth Institute of Biological Control, and the Agriculture
Canada Research Station at Belleville, Ontario) resulted in the shipment of
parasitoids by air from Japan to New Brunswick in 1970-75 (Tables 73 and 74). Further,
a small collection of parasitoids from C. murinana in Czechoslovakia was shipped to New
Brunswick in 1972. These introductions are detailed below.
In the early 1970s, the theory that spruce budworm epidemics may start in isolated
local epicentres led to interest in methods of quelling incipient outbreaks over small
areas. At the Laurentian Forest Research Centre this interest developed into a research
study of the native egg parasitoid, Trichogramma minutum Ril., as a candidate for
inundative release, now briefly reported. As pressure to find a biological alternative to
Open releases and recoveries of parasitoids against Choristoneura fumiferana (Clem.)
Year of
Species and province Year Origin Number recovery
Agria housei Shewell 1971 Ontario (laboratory 2800 1971
New Brunswick culture) (14 adults)
Nil in 1972-73
Lissonota sp. 1973 Japan 59 Nil in 1974
New Brunswick