Assessment of the efficacy of BTI Larvicide, VectoBac 12AS® (BTI AM65-52) against “nuisance” flies at water treatment plants in North West England

Wenjere, S

Abstract

In treating wastewater using percolating filters, nature employs diverse biota, which includes
nematoceran larvae, to sustain filter function. This study sought to generate evidence on the
efficacy of a Bacillus thuringiensis var. israelensis-derived larvicide widely used in England for
the control of adult flies that emerge. This was in part-fulfilment of the European Union’s new
biocidal products licencing requirements.
Adult and larval fly counts of four species of “nuisance flies”, Limnophyes minimus, Metriocnemus
eurynotus, Psychoda alternata and Sylvicola fenestralis were monitored at two wastewater
treatment works (WWTW) in North West of England. At selected points relative to peak fly
presence, selected filters were treated with the larvicide at concentrations of 80mg/L (low dose),
160 mg/L (medium dose) or 230 mg/L (high dose). Fly reduction and effectiveness of different
doses were determined based on pre- and post-treatment counts.
A single treatment against S. fenestralis using the medium (recommended) dose achieved 100%
larval and adult fly reductions within two and fourteen days respectively. Two treatments against
P. alternata at the low (recommended) dose achieved 93% and 95% larval and adult reductions
overall, 48 hours and 23 days after the second treatment respectively. Forty-eight hours and one
month after second treatment, larval and adult L. minimus respectively showed 100% and 30%
overall reductions at low dose, 100% and 91% at medium (recommended) dose and, 100% and
90% at high dose. At similar post-treatment points, larval and adult M. eurynotus showed 100%
and 94% overall reductions respectively at low dose, 97% and 99% at medium (recommended)
dose and 100% across both larvae and adults at high dose.

The biolarvicide showed no effect against non-target organisms but was harmful and effective
against target-species. Reduced and increased treatment strengths trialled against chironomid
species showed slightly reduced efficacy and no added benefit respectively.

Citation

Wenjere, S. Assessment of the efficacy of BTI Larvicide, VectoBac 12AS® (BTI AM65-52) against “nuisance” flies at water treatment plants in North West England. (Dissertation). University of Salford

• Thesis Type: Dissertation
• Deposit Date: Feb 19, 2018
• Publicly Available Date: Feb 19, 2018
• Additional Information: Projects : Assessment of the Efficacy of BTI Larvicide, VectoBac 12AS® (BTI AM65-52) Against “Nuisance” Flies at Water Treatment Plants in North West England.
• Award Date: Aug 21, 2017