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192 P. Harris
Releases and Recoveries
Table 49
Evaluation of Control Attempts
following screening studies by Hawkes & Mayfield (19780). The biology of this insect
is reported by Khan & Baloch (1976): the first two instars are leafminers; in the last
three, the larva lives outside the leaf in a case of hollowed leaves, and feeds by
protruding its head and forelegs through a hole in the leaf so that it continues to feed
inside the leaf. The insect overwinters as a larva inside the case attached to SaJsoJa
stems or stones. There are one to three generations a year in Pakistan, depending on
elevation. C. klimeschiella is established in California (Julien 1982).
The releases of both C. parthenica and C. klimeschielJa are listed in Table 49.
C. parthenica was released on a number of occasions in July and August in stands of
Russian thistle at the Regina and Swift Current Research Stations. The moths remained
on the plants where they were released for several days, but no eggs or larvae were
found in the vicinity. Larvae in the stems of potted plants that were placed outside failed
to complete development. The problem was presumed to be the cool summer temperatures
of the Canadian prairies. At Regina in July and August, the minimum temperature
was below the threshold for development for 50 days in July and August, and on 16
August, the temperature fell to 1.3°C. At all sites on the Canadian prairies, there is
normally less than the 500 degree-days required by the insect.
C. klimeschielJa was released in June at the Regina Research Station and bred in the
summer of release and the following summer. The population was less than one larva per
Russian thistle plant and they did no appreciable damage. In the spring of 1979, the
release site was flooded for several weeks in the spring and the colony was destroyed.
Open releases and recoveries against SaJsola pestifer A. Nels.
Year No. of moths released Source Release site
Coleophora parthenica
1975 273
1975 66
1975 33
Coleophora klimeschiella
1977 91
California
California
Pakistan
Swift Current. Saskatchewan
Regina. Saskatchewan
Regina. Saskatchewan
California Regina, Saskatchewan
ex Pakistan
Recovery
bred in 1977
and 1978 but
not in 1979
Summer temperatures on the Canadian prairies are too low for C. parthenica, and there
is no purpose in making additional releases unless a strain with a low temperature
threshold can be found. Even if such a strain can be established in Canada, on the basis of
results in the United States, the density of Russian thistle is unlikely to be affected.
C. klimeschiella can survive in Saskatchewan and hence presumably elsewhere in
southern Canada. Insects released for the biological control of a weed often require
several years for the selection of a strain adapted to the region, so the lack of a rapid
increase in the population should not be the sole reason for discontinuing further