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Impact of a potential chironomid (Diptera: Chironomidae) control agent, pyriproxyfen (S-31183), on indigenous non-target aquatic organisms.

Trayler, Kerry Mandy (1991) Impact of a potential chironomid (Diptera: Chironomidae) control agent, pyriproxyfen (S-31183), on indigenous non-target aquatic organisms. Honours thesis, Murdoch University.

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The juvenile hormone mimic, pyriproxyfen, 2-[1-methyl-2-(4- phenoxyphenoxy) ethoxy] pyridine, is considered to be an effective alternative to the organophosphate larvicide, temephos, for the control of chironomids (Diptera: Chironomidae) in the wetlands of Perth, Western Australia. The effects of this compound on non-target organisms which occur in chironomid habitats were investigated.

One species of fish and five indigenous, freshwater invertebrate species were exposed to pyriproxyfen for 48 hours in acute laboratory tests. Median effective and median lethal concentrations were between 8 and 621 times the concentration of pyriproxyfen (0.01 ppm) required to control the emergence of some nuisance chironomid species. Chronic toxicity tests indicated that 0.01 ppm pyriproxyfen did not affect the emergence of the mayfly, Cloeon fluviatile, or influence the growth of the freshwater algae, Chlorella emersonii. However, continuous exposure to pyriproxyfen (0.01 ppm) during a 3 brood, 14 day life cycle test, suppressed the growth of the cladoceran, Daphnia carinata and reduced reproduction by as much as 80%.

Two separate in situ enclosure experiments at North Lake and Lake Monger were performed to evaluate the effects of pyriproxyfen (0.01 ppm) on invertebrate fauna under natural conditions. Neither the macroinvertebrates, nor the zooplankton examined during these trials were affected by the pesticide. Daphnia carinata was not affected by the pyriproxyfen under these conditions. In addition, the emergence of two non-target insects, the mayfly, Tasmanocoenis tillyardi and the caddisfly, Ecnomus pansus did not appear to be affected by this pesticide. This study has shown that, at the rate required to control chironomids, pyriproxyfen had minimal impact on those species examined. Therefore, pyriproxyfen appears to be a relatively 'safe' alternative to temephos for the short-term control of chironomids in Perth wetlands until longer term, non-chemical control can be implemented.

Item Type: Thesis (Honours)
Murdoch Affiliation(s): School of Biological and Environmental Sciences
Notes: Note to the author: If you would like to make your thesis openly available on Murdoch University Library's Research Repository, please contact: Thank you.
Supervisor(s): Davis, Jenny
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