Control Options |
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Chemical ControlS-methoprene S-methoprene is a pesticide that acts as a juvenile hormone mimic disrupting the development of insects and preventing the larvae from emerging as adults. Used primarily in mosquito management, S-methoprene also has the potential to provide control against midge (Ali 1981; Lothrop and Mulla 1998). Although s-methoprene is perceived as being less toxic to non-target organisms than Abate, current research indicates that previous short-term studies may need to be reconsidered in light of more recent longer-term investigations. Hershey et al. (1998) studied the long-term effects of s-methoprene on 179 genera of insects in 27 wetlands in Minnesota and found that taxa richness was significantly reduced in the second year of s-methoprene application. Toxicity to, and interference with larval development has also been reported for a wide range of crustaceans including Daphnia sp. (Olmstead and LeBlanc 2001), copepods (Bircher and Ruber 1988), Palaemonetes sp. (shrimps) (McKenney and Matthews 1990) and brine shrimp larvae (Ahl and Brown 1990). Walker et al. (2005) found that s-methoprene had adverse effects on lobster larvae and Horst and Walker (1999) reported that s-methoprene delayed the moulting of blue crabs (Callinectes sapidus) and resulted in the deaths of 80% of larvae after exposure for 10 days. The Environmental Protection Authority (USA) summarised available fish studies and concluded that s-methoprene is moderately toxic to warm water freshwater fish and slightly toxic to coldwater, freshwater fish (EPA 1991). The effects on Western Australian freshwater or estuarine fish species are unknown. S-methoprene is not currently registered for use in Western Australia. However, Terry Phillips from Pacific Biologics, the Australian distributor of s-methoprene, has communicated that the company is looking to conduct efficacy trials in Western Australia in summer 05/06, and has indicated that protocols for these could be developed in conjunction with the Midge Research Group. A search of the literature revealed over 550 journal articles relating to the effects of s-methoprene on aquatic and terrestrial organisms and plants. It is recommended that a comprehensive evaluation of the recent literature be conducted to determine the non-target impacts of s-methoprene when used at likely field application rates for midge control. It is also recommended that toxicity trials on local fauna to determine the potential effects on south-western Australian aquatic ecosystems be conducted if this chemical is to be considered for use. Terry Phillips has indicated that the APVMA registration procedure for s-methoprene will require toxicity testing on local aquatic fauna. Abate Abate (Temephos) is an organophosphate pesticide that has been used to control larval midges in wetlands on the Swan Coastal Plain for over thirty years. However, disadvantages with the use of Abate include problems with larval resistance, and deleterious effects on non-target species. There is also some evidence to suggest that Abate increases the growth rate of cyanobacteria (Birmingham and Colman 1976; Wurtsbaugh and Apperson 1978). Currently, regular use of Abate to control nuisance midge is being undertaken at only a few lakes in the Perth Metropolitan area. These include Lake Joondalup, Yangebup Lake, North Lake and Bibra Lake. Although an effective treatment in general, the use of Abate does not guarantee complete control of larval midge. Lund (2003) found that over a three-year period of Abate application at Lake Joondalup the percentage of larvae killed was highly variable. Lund (2003) suggested that the effectiveness of Abate at Lake Joondalup could be improved by:
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Updated : 23 June, 2009 |