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Introduction and General Information

"Biological control is the use of biological organisms, or their by-products, to control pests. Biocontrol is popular in theory, because of its potential to be host-specific virtually without non-target effects." (D67)

Prevention and control of arboviral diseases such as WNV infection is accomplished most effectively through a comprehensive integrated mosquito management program; effective mosquito control begins with a surveillance program that targets pest and vector species, identifies and maps the habitats of the immature forms (larvae and pupae) by season, and documents the need for control.

  • Vector control is most effective when directed at the species responsible for virus transmission. For optimum impact both enzootic/epizootic and epidemic vectors should be targeted. (P32.1.w3)
  • Biological control (biocontrol) may be used as part of an integrated mosquito management program.
  • The role of biocontrol in the control of mosquito vectors may expand in the future.

(J84.7.w35, D67, D147)

Published Guidelines linked in Wildpro

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Microbial Larvicides

Microbial larvicides are generally employed in a similar manner to chemical larvicides (B250, W175.Nov01.WNV2). They may be used in ornamental pools in some circumstances. (W175.Nov01.WNV2). Further information on the application of larvicides is given in Chemical Control for West Nile Virus

Microbial larvicides such as Bacillus thuringiensis var. israelensis and Bacillus sphaericus can be used successfully in a broad range of freshwater habitats, but are somewhat unpredictable in salt marsh habitats.(D72)

  • Bacillus thuringiensis israelensis (Bti) (trade names Aquabac, Bactimos, LarvX, Teknar, Dunks) is available in water-dispersible granule, aqueous suspension, pellet, granule and briquette formulations. Applied against larvae, its main advantages are non-target safety and that briquettes can provide control for thirty days or longer, while the main disadvantages are a short window of opportunity for treatment and lack of efficacy against pupae. (J84.7.w35)
    • This larvicide is relatively ineffective in nutrient-rich (highly organic) waters. (P32.1.w8)
  • Bacillus sphaericus (Bs) (trade name VectoLex) is available in granular and water-dispersible granule formulations. Applied against larvae, its main advantage is non-target safety while its main limitations are a lack of efficacy against pupae and that it only works in fresh water and not in brackish water. (J84.7.w35)
    • This larvicide is effective in nutrient-rich polluted waters. (P32.1.w8)
    • This larvicide is preferentially targeted at second and third instar larvae, therefore the treatment window is limited. (D73)
  • Both of these larvicides are considered to among the most selective and least hazardous pesticides. In many situations microbial larvicides can be used quite safely. (P32.1.w8)
  • Microbial larvicides are short-lived in the environment. (P32.1.w8)
  • Contact with broken skin and significant inhalation should be avoided. (P32.1.w8)

More details regarding these biorational larvicide preparations are provided in:

Associated techniques linked from Wildpro

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Larvivorous Fish

Predacious fish which feed on mosquito larvae may be used for the control of mosquito larvae in ponds and other permanent or semi-permanent waterbodies; a variety of species have been suggested for this purpose.
  • Use of larvivorous fish can be extremely effective in areas where water quality permits their use. (P32.1.w8)
  • Preference should be given to the use of locally native fish species, therefore the most appropriate species to use will vary depending on the geographical region.
  • Native larvivorous fish play an important role in the utility of open marsh water management and rotational impoundment management for mosquito control. In the USA fish species playing such a role include Fundulus spp. and possibly Rivulus spp. (J84.7.w35)
  • It is important to remember that predacious fish do not feed exclusively on mosquito larvae; they also may eat various aquatic insects, tadpoles, fish eggs and fry and zooplankton. (J84.7.w35)
  • It may be possible, for the purpose of stocking an ornamental pond with predaceous fish, to collect mosquito fish such as Gambusia affinis and Gambusia holbrooki from local streams; alternatively they may be purchased. (J84.7.w35, D67, D71, W175.Nov01.WNV2)
  • Other predatory fish include the Argentinean pearl fish, Cynolabias belloti, which may be particularly useful in ponds which dry periodically, as their eggs survive this process and hatch when the pond floods once more. (D71)
  • Introduction of fat-headed minnows to permanent water bodies has been used for mosquito control in zoos. (P30.1.w1)

(J84.7.w35, D67, D70, D71, D72, D147, P32.1.w8, P32.1.w27, W175.Nov01.WNV1, W175.Nov01.WNV2)

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Potential Biological Control Measures

There are a variety of biological control measures which have been used or researched for use against arthropod pests. It is possible that their application against mosquitoes may increase in the future.

Releasing sterile males in order to control an arthropod is known most widely for its successful application to control of the screw-worm fly Cochliomyia (Callitroga) hominivorax in the USA. (B46)

  • A successful experiment to eliminate a population of Culex pipiens quinquefasciatus mosquitoes from an island by release of sterile males has been described (D71).
  • Control of Culex pipiens quinquefasciatus by importation of a strain with "cytoplasmic incompatibility", resulting in intersterility has also been described in the control of this mosquito vector of filariasis in Burma. (D71)

Use of a variety of other biological control methods including predatory mosquitoes such as Toxorhynchites spp., dragonfly nymphs, predacious copepods such as Mesocyclops longisetus, parasitic nematodes (Romanomermis spp.), a pathogenic protozoon Nosema algerae, and a fungus Laginidium giganteum have been tested for use in mosquito control. These have not been widely used to date, although Laginidium giganteum has been registered for mosquito control (under the trade name "Lignex") by the Environmental Protection Agency.

  • A cyclopoid copepod Macrocyclops albidus (Jurine) (Crustacea - Crustaceans and Pentastomes (Phylum-Division)) is under investigation for use as a mosquito control agent in Florida. Laboratory trials indicate that it is an efficient predator, particularly on larvae of one to four days old, reducing populations by 90%. It is also considered to be able to establish itself and maintain populations under a variety of conditions. (W477.Jan04.wnv2, W478.Jan04.wnv1)

(J84.7.w35, D67, D147, W175.Nov01.WNV1, W477.Jan04.wnv2, W478.Jan04.wnv1)

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Authors & Referees

Authors Debra Bourne (V.w5)
Referee Suzanne I. Boardman (V.w6); Becki Lawson (V.w26); Dr Robert G. McLean (V.w42)

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