Prickly Pear, the Other Face of Cactus Pear

摘要

Several tree-like opuntiae have been introduced from Central America to many parts of the world with compatible climates. Opuntia ficus-indica is the most widely cultivated for its fruit and as a source of fodder. Easiness of vegetative propagation incombination with high seed production and the absence of cactophagous natural enemies outside its native range, are the attributes which facilitated its rapid spread. Although only the spineless varieties were initially established, the species gradually reverted back to the spiny wild genotypes, now known as prickly pear, through genetic recombination and selected grazing pressure. This led to serious invasions in many countries over a period of 100 to 200 years. Such invasions occurred in Australia,South Africa, Mauritius, Hawaii, Madagascar, Ascension Island, Ethiopia, Eritrea and Yemen. The threat to the natural resources caused by prickly pear invasions became so grave that full-scale biological control programs had to be initiated. This led tothe introduction of several natural insect enemies to Australia, South Africa, Mauritius, Hawaii and other countries. These biological control programs were highly successful in reducing invasions while commercial cultivation of the benign cultivars could continue. Such drastic actions are, however, not considered in other countries such as Ethiopia, Eritrea, Yemen and Madagascar, where the emphasis in managing invasive prickly pears has shifted to improved resource utilization and value-adding initiatives. Hopefully the additional income will lead to poverty alleviation and provide farmers with the necessary financial resources to control unwanted invasions. The indigenous knowledge of cactus pear in countries like Mexico has become the key to the success of this approach. Time will tell if this will succeed in reducing invasions during the next century.