The bio-ecology and control of Coproica vagans and Coproica hirtula (diptera: Sphaeroceridae) in cattle feedlots

[摘要] English: Sphaeroceridae are generally known as lesser dung flies. These are small to mediumsized dark-brown to blackish flies ranging from about 0.5 mm to 6 mm in length. Theyare saprophagous and occur throughout the tropical and subtropical regions of theworld. A unique scenario involving Sphaeroceridae flies that constitute a seriousproblem at South African feedlots is discussed. Two species, namely Coproica vagans(Haliday) and Coproica hirtula (Rondani) are both associated with cattle dung atfeedlots, with the former species reflecting dominance. The flies cause a nuisance tothe cattle by forming black clouds of swarming flies. It therefore became imperative tofind a way to control these flies. The establishment of separate sphaerocerid laboratorycolonies from which experimental studies could be conducted was successful and isdescribed.The seasonal occurrence and relative abundance of the Diptera fauna occurring withinundisturbed cattle droppings exposed to shaded and sunny locations in the central FreeState was investigated. The Sphaeroceridae was of particular interest, but only fivepresumably new species were discovered among the 21 fly species reared from thesedroppings. No C. vagans or C. hirtula specimens were encountered.The influence of physical parameters such as temperature and moisture content of thedung on the development and survival of immature stages and adult flies is described.Temperature had a major effect on all stages of both species, and both too low and toohigh temperatures led to severe mortality. Optimum developmental temperatures werebetween 24°C and 30°C. The development time of all stages also increased with adecrease in temperature. Moisture content of the dung had the same influence on allstages of the Sphaeroceridae, and optimum moisture content levels were atapproximately 90%. Development times also increased somewhat with a decrease inmoisture content levels of the dung. Oviposition by adult females of both sphaeroceridspecies and the influence of temperature and photo periodicy was determined and isdescribed. Oviposition continued for more than 60 days at colder temperatures,although the number of eggs produced was often very low. Higher temperatures on theother hand resulted in large numbers of eggs produced by sphaerocerid females (up to607 eggs per female) at 24°C, but the duration of oviposition dropped. Differentphotoperiods had no severe effect on oviposition or egg production. Development andsurvival of immature stages and adult Sphaeroceridae were also influenced by the typeof dung which they were offered and the effect of this phenomenon on the flies is alsodescribed. Some dung types, e.g. horse, buffalo and rhino dung, had a negativeinfluence on larval and adult survival most probably as a result of the higher fibercontents of these dung types. The other dung types such as cattle, sheep and elephantdung, led to successful development and survival of all stages.Biological control was attempted with several Coleoptera (a staphylinid, Philonthuscaffer (Boheman) and scarabaeids Aphodius pseudolividus Balthasar and Harmogasterstrydomi Endrëdi), Diptera (Musea xanthomelas Wiedemann and Coboldia fuscipes(Meigen)) and mite species. These biological control agents all failed to controlSphaeroceridae numbers mainly because of their inability to survive in wet feedlotdung. Chemical control on the other hand produced positive results and seemed like theonly option available. Several insecticides and chemicals were tested but only two,namely Neporex (cyromazine) and Scatterkill (piperonyl butoxide), showedirradication potential. A further advantage of Scatterkill is its long residual effect infeedlot dung.

[发布机构] University of the Free State