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180 P. Harris
Background
Table 47
most areas it was less abundant in the early 1970s than it had been in 1956 and that
toadflax was not a serious problem in cereal crops. In creeping red fescue, 180 toadflax
stems/m 2 reduced the yield by a third; but in most areas there were 20 or less stems/m 2
with no measurable effect on yield. Most of the dense stands of the weed were on sites
that had been cleared and abandoned or were cropped infrequently.
In Saskatchewan, the weed is still dense on uncultivated sandy soils from North
Battleford west to Alberta. In other regions of the province it has disappeared or greatly
declined since the 1950s.
The decrease in the importance of the weed is reflected by the decline in the number of
abstracts relating to its chemical control in the Research Report of the Expert Committee on
Weeds (Canada Western Section) (Fig. 8). The decrease of the weed has not however
changed its status under noxious weed legislation. For example in Saskatchewan provincial
subsidies are still paid to municipalities for its control.
L. dalmatica (L.) is considerably more persistent that L. vulgaris, and it appears to
exclude most other herbaceous species from the stand. Stands are local and the total
area occupied does not appear to be large. Thus in the absence of documented evidence
it does not appear to offer a serious threat.
A more detailed history of the biological control of toadflax is given by Harris &
Carder (1971). The decline of the weed in western Canada coincided with the appearance
of the flower-feeding beetle Brachypterolus pulicarius (L.). This European
beetle was present in eastern Canada and spread to the west. In addition the seedfeeding
weevil Gymnaetron antirrhinii (Payk.), another European insect present in the
east, was released in western Canada in 1957. Both insects are now present in regions of
western Canada where toadflax is common.
In 1962, a European defoliating moth, Calophasia lunula (Hfn.), was first released in
Canada, and it became established on the railway right-of-way at Belleville, Ontario in
1966. The moth has two overlapping generations and lays single well distributed eggs.
The first two larval instars are inconspicuous and frequently feed inside the flowers, but
the third to fifth instars feed externally on the foliage and are easily seen. Samples taken
along the railway right-of-way (Table 47) indicate that larvae were present from late May
to early September, usually at a density of 2-6 larvae/100 stems regardless of the
toadflax density. The density of the toadflax increased greatly following soil disturbance
in the previous year. The overall level of damage was not impressive with less than 20"10
of the stems being defoliated.
Density of C. lunula and toadflax, L. vulgaris Mill. and L. dalmatica (L.) Mill .• along
the railway at Belleville. Ontario.
No. 3rd-5th instar
Date No. samples· No. Toadflax stemsfm Z C. lunula larvae/m 2
2 Jun 1968 26 85.7 2.0
8 Aug 1968 19 89.1 3.8
3 Sep 1969 158 6.6 0.05
18 Jun 1970 52 7.2 0.31
13 Aug 1970 205 0.98
15 Aug 1971 31 7.7 0.13
• (0.25 m 2 ) samples taken at 5 pace intervals