Biological control is the use of biological agents (fish, pathogens, insects, plants…) to combat unwanted exotic species.

It is an effort to restore the ecological system of checks and balances. Most often, but not always, biocontrol agents are also exotic, making biocontrol a somewhat risky option. Most often, but not always, biocontrol agents are also exotic. Researchers travel to the countries of origin of the plants to find agents that naturally attack the unwanted species. These agents are tested in quarantine for “host-specificity,” in other words, will they consume only the target exotic invasive species, or native species too? Successful candidates eventually are released into their new environments. Sometimes the biocontrol agents are successful, sometimes not.

In the case of non-indigenous aquatic and wetland weeds, biological control insects have been tested and utilized since the 1960s.

Image: Salvinia Weevil The tiny salvinia weevil is a very effective biocontrol agent.
Image: Hydrilla damage Visible damage to hydrilla leaves from the effects of the leaf-mining hydrilla fly.

For more information on the plants and biocontrol insects that have been used against them, click the links below:

  • Alligatorweed
    (Alternanthera philoxeroides)

  • Brazilian pepper tree
    (Schinus terebinthifolius)

  • Broadleaf dock
    (Rumex obtusifolius)
  • Curled dock
    (Rumex crispus)
  • Eurasian water milfoil
    (Myriophyllum spicatum)
  • Giant sensitive plant
    (Mimosa pigra)
  • Groundsel bush
    (Baccharis halimifolia)
  • Hydrilla
    (Hydrilla verticillata)
  • Kariba weed
    (Salvinia molesta )
  • Melaleuca
    (Melaleuca quinquenerva)
  • Nut sedge
    (Cyperus rotundus)

  • Purple loosestrife
    (Lythrum salicaria )

(Source: University of Florida Center for Aquatic and Invasive Plants http://aquat1.ifas.ufl.edu/biocontrol.html)