Insects
The reason insects are often good biological control agents is that they have great diversity,
high degrees of host specialisation and intimate adaptations to hosts. Examples of successful programs include
Cactoblastis cactorum (moth) on several cacti, Chrysolina
quadrigemina (beetle) on
St John's wort and Cyrtobagous salviniae (weevil) on
salvinia.
Fungi, mites, nematodes
Rusts such as Puccinia chondrillina have been used to control several weed species such as skeletonweed
(Chondrilla juncea). Other agents include Collectotrichum
gloesporioides f.sp. aeschynomene, an agent to control northern jointvetch
(Aeschynomene virginica). Mites and a nematode have also been released to control particular weeds.
Fish
Some species of fish have been released specifically to control aquatic weeds. Others are used as
multi-purpose weed control agents and food sources.
