pdf, 57.71Mb - Entomological Society of Canada
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118 P. Harris<br />
Table 23 Open releases and recoveries <strong>of</strong> R. conicllS Froel. against Cardlllls spp.<br />
Release Initial<br />
Province Host date Place Source Number recovery<br />
Saskatchewan C. "Ulans 26.7.68 Aylesbury 400 1969<br />
16.7.69 1898<br />
C. "Ulans 16.7.69 Findlater 1897 1969<br />
Ontario C. acamhoides 25.7.68 Read (site A) 320 1969<br />
23.5.69 1 282<br />
10.6.70 2 350<br />
5.10.69 Read (Site B) 3 74<br />
5.10.69 1 80<br />
31.6.70 Read (Site C) 1 3500 1971<br />
22.5.69 Stoco Lake 1 350 1970<br />
11.7.69 Roslin I 4320 1970<br />
22.5.70 1 1500<br />
1.5.70 Moira 4 200<br />
C. acamhoides 3.6.70 Flesherton 1 250 not checked<br />
xc. "utans<br />
C. "ulans 9.6.75 Guelph 5 2185 1976<br />
Manitoba C. "Ulans 17.6.74 Somerset 5 500 1975<br />
4.9.74 Darlingford 5 4000 1975<br />
Quebec C. "ulans 17.6.74 Lac St-Jean 5 1100 1975<br />
C. acanthoides 23.7.78 Huntingdon 5 7731 1982<br />
16.6.80 5 10130<br />
British Columbia C. nUlans 16.7.79 Williams Lake 5 2600 site<br />
destroyed<br />
1. Mulhouse, France ex C. nutans<br />
2. St. Hippolyte, France ex C. personala<br />
3. Krymsk, USSR ex Cirsium spinosllm<br />
4. Nantes, France ex C. vulgare<br />
5. Findlater. Saskatchewan ex C. nutans<br />
range <strong>of</strong> the strain introduced is more restricted than that <strong>of</strong> R. conicus. Under field<br />
conditions in Virginia, United States, it had a strong preference for C. nutans over C.<br />
acanlhoides and was more readily established on stands <strong>of</strong> the former species (Sieburth<br />
& Kok 1982). On C. nUlans, high densities <strong>of</strong> T. IIOTTidus and R. conicus were found in<br />
the same stands (Kok 1980).<br />
In <strong>Canada</strong>, the adult weevil overwinters in the soil litter. It becomes active in early<br />
spring to lay in the mid-vein <strong>of</strong> large CardullS leaves. This differs from the life cycle in<br />
Rome, Italy, where the weevil starts ovipositing in October and continues over winter<br />
(Bolt & Campobasso 1981). The larva bores down the mid-vein into the crown and<br />
develops just below the apical leaves. This causes the plant to produce several lateral<br />
shoots, which in Saskatchewan may be attacked again when about 15 cm high; the larvae<br />
are also sometimes found in the lateral vegetative buds. The result is to produce a bushy<br />
thistle in which flowering is probably delayed. The larvae pupate in the soil and emerge<br />
as adults in reproductive diapause in the early summer. They feed on the thistle leaves<br />
until the fall and can be frequently found on the bracts <strong>of</strong> the flower buds.<br />
(b) Releases<br />
The stock released at Aylesbury, Saskatchewan, was collected in eastern Austria. around<br />
Morel, Switzerland, and Neuenburg, Germany (Table 24). In addition, 22 weevils from
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