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Releases and Recoveries
Table 51
Scmc/lus an'ens;s L.. 207
T. dilacerata has been released on a total offive sites in Saskatchewan in 1979. 1980. and
1981. and one site each in Alberta. Quebec. and Prince Edward Island (Table 51).
Breeding occurred in 1979 when the flies were released in large field cages (180 cm high.
180 x 180 cm). At Estevan three galls were found in August and 250 at Regina. From the
latter an estimated 1150 flies emerged in the cage at Regina. Many of these were allowed
to escape so that they could search for overwintering sites but no survivors were found
in 1980. In 1981. only three galls were found in Outlook and 22 at Wishart. Saskatchewen.
However. 98% of the flies were released for overwintering in the fall of 1980 and 97% in
1981. All fall releases were made with flies that emerged from galls collected in Austria.
In 1980. the flies emerged in the quarantine laboratory in a 16 hour day except for 1000.
which had emerged in an eight hour day at 14°C and were released into a large field cage
at Regina. Saskatchewan in September 1980. A log pile covered loosely with straw was
provided as a possible overwintering site. The cage was removed in late fall to allow
additional insulation by snow and replaced on 15 April 1981. No flies emerged.
Subsequently it was learned that flies emerging at room temperature in a 16 hour day
do not enter diapause. Releases made in the fall of 1981 were all made with flies conditioned
for overwintering.
C. sonciJi was released on four sites in Saskatchewan in 1981. where it survived the
first winter on two sites and produced two generations in 1982 (Table 51). The colony in
Alberta produced galls in 1981 but did not survive the winter. No galls were found from
the 1982 release in Alberta nor from the 1981 and 1982 releases in Manitoba and Quebec.
Open releases and recoveries against Sonchus arvensis L.
Species and Province
Tephritis dilacerala Lw. *
Saskatchewan
Alberta
Quebec
Prince Edward Island
Cysliphora sonchi (Bremi)*
Saskatchewan
Alberta
Manitoba
Quebec
Total
Total
Year Number
1979 810
1980 11486
1981 1093
1981 2000
1981 1947
1981 2000
19336
1981 21900
1981 5000
1982 4500
1982 2000
1981 5000
1982 2100
40500
Year of Recovery
1979
1982
1981
* All insects were originally collected in Austria. All C. sonchi and 6% of the T. dilacerala
releases were made with laboratory reared stock. and the remaining T. dilacerala releases
were made with flies that emerged from pupae collected in the field in Austria.