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Chrysolina hypericJ
(Forester)
(Coleoptera:
Chrysomelidae)
Ilypericum perfOrUlIlm L.. 173
adjust in this manner bodes well for its survival in the varied conditions at Cranbrook.
British Columbia.
In France, A. chloris can be heavily parasitized by Ap/,idius cardui Marsh. (Braconidae)
and Aphidencyrtus aphidiverus Mayr. (Encyrtidae), but its reproductive capacity is
such that it remains a common species (Wilson 1943). The stocks of A. chloris received
from the Rhine Valley and Alsace contained Lysiphlebus faborum (Marsh.) (Braconidae).
This is an aggressive parasitoid and if left unchecked can destroy a laboratory colony.
Although A. chloris will attack various species of Hypericum, the damage done to the
plant or its acceptance by the aphid varies with the species. For example, at the end of 5
days the number of offspring from two mature apterous females on H. perforatum. H.
rhodopaeum, H. calyeinum, and H. densiflorum were 37, 10, 7, and 0, respectively.
Large colonies of A. chloris consistently killed vigorous plants of H. perforatum in
about a month, while H. rhodopaeum lived for over seven months and put on new
growth in spite of a heavy aphid population.
(b) Releases
Two releases of A. chloris were made in the Cranbrook, British Columbia, area (Table
45). Infested H. perforalum plants were transplanted into the field. In 1979 this was done
during a period of drought: the transplanted plants died and most of the surrounding H.
perforatum had lost their foliage. No evidence of aphid survival was found. In 1980
infested plants were transplanted earlier in the spring and the aphids moved readily onto
the surrounding plants. By early November all of the rosettes sampled in a 20 m radius at
the two release sites had a few fundatrigeniae and/or eggs. By late June 1981 following a
wet and cool spring, scattered plants within a radius of 50 m of the release point had
small colonies of A. chloris near the flower buds. By far the strongest colony of the aphid
was on the site least favoured by C. quadrigemina.
British Columbia was used as a source for obtaining stock for release in Ontario, Nova
Scotia, and New Brunswick (Table 45).
In Ontario, C. hyperici became established at the release site near Picton. Overwintering
survival was 63% for adults and 31% for eggs compared to 19% and 6%
respectively, for C. quadrigemina (Harris & Peschken 1974). Nevertheless C. quadrigemina
rapidly became the most common species, although both species were still
present in 1979 (13 ddand4 22 C. quadrigemina:4 ddand 322 C. hypericiin the sample
collected).
The releases in Nova Scotia contained a few individuals of C. quadrigemina collected
with the C. hyperici from Fruitvale, British Columbia. Both species became established
but by 1979 C. hyperici had become numerous enough at one site in the Annapolis Valley
to generate one query about the identity of the beetles sitting on the side of a house (H.
Specht, 1979, personal communication). This was about 30 km from the release site.
According to M. Neary (1979, personal communication), the original release site has
been cleared of the weed and it has been substantially reduced in the Kingston-Auburn
area. C. hyperici is also established in the Dundurn and Fenwick regions. At Dundurn
between 1970-72 the number of flowering stems declined from 5.8 to 3.4/m2. This is a
more gradual decline than has been usual with C. quadrigemina in British Columbia.
C. hyperici released at Tay Creek, New Brunswick, were well established in 1977, but
were not numerous enough to control the weed. A problem with the release made in 1975
is that all the individuals examined were female. Apparently the females continued their