Biological control of plants has generally been

much more successful than biological control of

animals, because most plant feeders are much

more specific in their diet than most predators.

A notorious historical failure of biological control

of animals was the introduction of the South

American Cane Toad into Australia to control the

sugarcane beetle Dermolepida albohirtum. The toad

was a totally inappropriate biological control

agent, since it feeds indiscriminately on a wide

range of insects, arthropods, and even small

mammals, reptiles, and amphibians.

Furthermore, it is toxic, and therefore

dangerous to native predators such as

monitor lizards and snakes that try to

eat it. It remains a serious invasive in

Australia to this day; it was also not

very effective at controlling the

sugarcane beetle.

above | Agasicles hygrophila

(Chrysomelidae) The Alligator Weed

Flea Beetle was introduced to Florida

to control the invasive alligator weed

that was blocking waterways.

right | Nanophyes marmoratus (Brentidae)

A European weevil successfully introduced

to North America to control the flowering

plant European purple loosestrife.