pdf, 57.71Mb - Entomological Society of Canada
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184 M. G. Maw<br />
Discussion<br />
Recommendations<br />
Literature Cited<br />
obtained from the high altitude valleys <strong>of</strong> Jujuy province in Northern Argentina for<br />
screening at Regina. The two species fed on local prickly-pear, but it was necessary to<br />
injure the pads before the larvae would enter to feed. Once inside, the larvae completely<br />
hollowed the pads, but then would not leave them to attack new ones. Either the local<br />
cactus was unsuitable or the insects were diseased for both species became weak and the<br />
colonies died out after a few generations in the laboratory.<br />
No introductions <strong>of</strong> cactus insects are considered, for any harm or inconvenience<br />
caused by our prairie cactus is balanced by benefits from it. The native biotic agents<br />
exert considerable pressure on the cactus and our native grasses, when not overgrazed<br />
are well able to compete.<br />
Any release <strong>of</strong> biological control agents to control prickly-pear would be vigorously<br />
opposed by both the United States and Mexico, because Opuntia spp. are used as<br />
emergency fodder for cattle and as human food. In addition, at least one species <strong>of</strong><br />
Opuntia is listed as endangered and 12 as threatened and still others are valued as<br />
ornamentals throughout the American southwest.<br />
(I) Introduction <strong>of</strong> biological control agents for Opuntia spp. in <strong>Canada</strong> should not<br />
be pursued.<br />
(2) Any control <strong>of</strong> cactus in <strong>Canada</strong> should be approached as a range management<br />
problem.<br />
Bement, R.E. (1968) Plains prickly-pear; relation to grazing intensity and blue grama yield on Central Great Plains. Journal <strong>of</strong> Range<br />
Matulgement 19, 83-86.<br />
Houston, W.R. (1963) Plains prickly-pear, weather, and grazing in the Northern Great Plains. Ecology 44, 569-574.<br />
Hunter, W.O.; Pratt, F.C.; Mitchell, J.D. (1912) The principle cactus insects <strong>of</strong> the United States. USDA Bureau <strong>of</strong> Entomology 113. 1-71.<br />
Mann, J. (1969) Cactus-feeding insects and mites. Smithsonian Institute Bulletin 256, 158 pp.<br />
Martin, A.C.; Zim, H.S.; Nelson, A.L. (1961) American wildlife and plants. A Guide to wildlife food habits. New York, Dover Publications<br />
Inc., 500 pp.<br />
Maw, M.O.; Molloy, M.M. (1980) Prickly-pear cactus on the Canadian prairies. Blue Jay 38, 208-211.
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