One of the most famous biological control example was in Australia, where the prickly pear cactus (the pest) of North America was first introduced into gardens and escaped into the countryside and flourished under the Australian climate system. The cactus started to cover a good deal of agricultural land and was necessary to get rid of it, however, there was no natural herbivore of the cactus so an alien specie (non-native specie) was introduced from another country which was a moth (Cactoblastis). This moth was introduced and had no competitors so they started to remove the prickly pear cactus.
- No toxic chemicals involved
- Less impact on man or the impact
- Not 100% effective
- Often difficult to control, there is often a danger that the alien specie would start preying on native species, causing native specie population to diminish
- Difficult to match a predator to the prey which can effectively remove the pest
- This process may last a long time