Example of Regulation of Host Population by a Herbivore

In the 19th century, prickly pear cactus, Opuntia sp. was introduced into Australia from South America. Because no Australian predator species existed to control the population size of this cactus, it quickly expanded throughout millions of acres of grazing land.

The presence of the prickly pear cactus excluded cattle and sheep from grazing vegetation and caused a substantial economic hardship to farmers.

A method of control of the prickly pear cactus was initiated with the introduction of Cactoblastis cactorum, a cactus eating moth from Argentina, in 1925. By 1930, densities of the prickly pear cactus were significantly reduced.

In the 19th century, prickly pear cactus, Opuntia sp. was introduced into Australia from South America. Because no Australian predator species existed to control the population size of this cactus, it quickly expanded throughout millions of acres of grazing land.