The efficacy of two novel insecticides to control nuisance diptera breeding in sewage biological filters

This thesis investigates the potential of two novel insecticides for the control ofnuisance Diptera emanating from sewage biological filters. The efficacy of the insectgrowth regulator pyriproxyfen and a biological nematode Steinernema feltiae for thecontrol of sewage flies were assessed. Both insecticides targeted primarily Sylvicolafenestralis, but also the chironomids Metriocnemus hygropetricus and Limnophyesminimus. Initial laboratory studies determined that concentrations of pyriproxyfen greater than 0.2 mg l-1 inhibited insect egg development or hatching and survival to thefirst larval instar. Four trials, assessing the efficacy of pyriproxyfen as the formulationSumilarvoo were undertaken. Significant (P<0.05) reductions in the emergence of S.fenestralis adults were achieved for doses of 0.5mg L-1, 0.22mg L-1 and 0.2mg L-1 butnot for 0.4mg L-1. Reductions ranged from 38% to 100%. There is evidence to suggestthat pyriproxyfen may affect adult control over two generations but it may have alimited window of use when targeting adult control. The Chironomid L. minimus wasalso effectively controlled (P<0.05) with up to 70% suppression of adult emergencedetected. High performance liquid chromatography (HPLC) was ascertained to be aneffective analyses tool in determining that pyriproxyfen has a high affinity for sewagesludge's and concentrations >100 mg L-1 inhibited aerobic and anaerobic purificationprocesses. Laboratory based pathogenicity tests determined that the nematodeSteinernema feltiae is a viable biocide capable of infecting the larvae of sewage flies.Field trials at three sites using a dose of one million nematodes per m2 producedsignificant reductions (P<0.05) in the emergence of S. fenestralis and Mhygropetricus. Reductions ranged from 25-67% and 25-91% respectively. No adverseeffects on the non-dipteran filter fauna, the purification efficiency, or the invertebratesin the river receiving the work's effluent, were detected after use of both insecticides.

Level dc:type.qualificationlevel

Doctoral (Level 8)

Year dc:date.issued

2006

Author dc:creator

• Cleworth, MA

Language dc:language

en

Identifier

oai:salford-repository.worktribe.com:1389510

OAI identifier oai:identifier

oai:salford-repository.worktribe.com:1389510