Efficiency of Bti-based floodwater mosquito control in Sweden – four examples

Publication Type:Journal Article
Year of Publication:2014
Authors:M. L. Schäfer, Lundström J. O.
Journal:Journal of the European Mosquito Control Association
Start Page:1
Date Published:03/2014
Keywords:Aedes sticticus, Bti, floodwater mosquitoes, mosquito control, treatment coverage, treatment efficiency

<p>Abstract: Mass-occurrence of floodwater mosquitoes, mainly Aedes sticticus, in the River Dal&auml;lven floodplains in central Sweden has caused public health issues and economic losses for many decades. In the summer of 2000, the problem escalated and the Biological Mosquito Control project was initiated with the aim of reducing mosquito nuisance. Larviciding, based on Bacillus thuringiensis israelensis (Bti), was chosen as the optimal method. However, high abundance of blood-seeking floodwater mosquitoes after Bti-treatments on some occasions raised questions about the effectiveness of the treatments. This study evaluated the effect of Bti-larviciding on abundance of larval and adult floodwater mosquitoes in four selected study areas, each represented by a CDC-trap site and a 5 km radius. The four areas differed with respect to their mosquito control history and the coverage of larval habitats with Bti-larviciding. The Bti-treatments provided a significant reduction of mosquito larval abundance, and normally 100% reduction was achieved. Thus, high abundance of blood-seeking mosquitoes could not be explained by insufficient larval control by Bti. However, a significant negative correlation was found between high numbers of blood-seeking floodwater mosquitoes and the coverage of larval habitats with Bti-larviciding within 5 km around the trap site. Consistently low numbers of mosquitoes (less than 1000 per trap/night) were only found in the two areas with high treatment coverage of larval habitats (97-100%). Evaluating the mosquito control efficiency showed that larval habitat coverage of at least about 95% is required in order to accomplish consistent low floodwater mosquito numbers. The conclusion from this analysis is that the coverage of larval habitats with Bti-larviciding in parts of the River Dal&auml;lven floodplains has to increase in order to guarantee an improvement of the public health problems caused by Aedes sticticus and other floodwater mosquitoes to both humans and animals in the region. Journal of the European Mosquito Control Association 32: 1-8, 2014</p>

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