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156 M. G. Maw
Discussion
Table 37
Table 38
chrysomelid. Ga/eruca TUfa Germ.; and a mildew. Erysiphe convolvuli DC.. showed the
most potential as control agents (Rosenthal 1980). None. however. was found to be
strictly monophagous.
Little biological control work has been done in Canada. However. limited attempts to
augment existing populations or to establish new colonies in Alberta and British
Columbia with insects from Saskatchewan and Ontario (Table 37 and Table 38) were not
successful.
Collection and release in Canada of chrysomelid insects in control of COlU'O/VIl/US arvensis
L. projects
Species Number Year Source Release or Lab Study
Chirida guttala 114 1969 Canada British Columbia (study)
(01.) 125 1970 Ontario British Columbia (study)
236 1979 Saskatchewan Alberta (release)
C/lelymorpha cassidea (F.) 97 1979 Saskatchewan Alberta (release)
Melriona bie%r (F.) 18 1969 Canada British Columbia (study)
7 1970 Ontario British Columbia (study)
Metriona purpurata Boh. 224 1979 Saskatchewan Alberta (release)
Collection and release in Canada of chrysomelid insects in control of Convo/vulus sepiwll
L. projects
Species
Chirida gllttala (01.)
Melriona bie%r (F.)
Number
120
200
Year
1971
1971
Source
Ontario
Ontario
Release
British Columbia
British Columbia
Bindweed competes with crop plants for nutrients and water, and thus lowers yields. It
twines around plants, smothering them and interfering with harvesting, and is a haven
for crop pests (Rosenthal 1980}. It is considered to be the 12th most important weed in
the world and the 14th most important weed in the United States (Rosenthal 1980). It is a
serious weed in Ontario and Quebec but a lesser problem in the western provinces. It is
mainly a weed in cultivated fields and so not a good candidate for biological control.
A large number of insects are associated with bindweed in North America. but only
sporadically in localized areas is appreciable damage done to the plant (Maw unpublished
data). Also, it appears that most insect damage occurs when bindweed is
supported by other plants or fences, rather than in the prostrate growth in fields.
Attempts to move Chirida gllliala, Melriona bicolor and M. purpurala, and Che/ymorpha
cassidea into new areas were unsuccessful. This may indicate that these species
have reached their geographic limits.
Rosenthal & Buckingham (1982) found a number of European organisms that may
be useful as control agents of bindweed in North America. Of these. the arthropods
Ga/eruca rufa, Spermophagus sericeus, and Eriophyes sp. probably have the most
potential (Rosenthal 1980) and several other species may also be useful (Rosenthal &