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. 2018 Jul 6;8(15):7563-7573.
doi: 10.1002/ece3.4250. eCollection 2018 Aug.

Microbial larvicides for mosquito control: Impact of long lasting formulations of Bacillus thuringiensis var. israelensis and Bacillus sphaericus on non-target organisms in western Kenya highlands

Yahya A Derua  1   2 , Samuel C Kahindi  3 , Franklin W Mosha  1 , Eliningaya J Kweka  4   5 , Harrysone E Atieli  6 , Xiaoming Wang  7 , Guofa Zhou  7 , Ming-Chieh Lee  7 , Andrew K Githeko  8 , Guiyun Yan  7
Affiliations

Microbial larvicides for mosquito control: Impact of long lasting formulations of Bacillus thuringiensis var. israelensis and Bacillus sphaericus on non-target organisms in western Kenya highlands

Yahya A Derua et al. Ecol Evol. .

Abstract

The microbial larvicides Bacillus thuringiensis var. israelensis and Bacillus sphaericus have been used extensively for mosquito control and have been found to be effective and safe to non-target organisms cohabiting with mosquito larvae. Recently developed long lasting microbial larvicides (LLML), although evading the previous challenge of short duration of activity, increase the risk of persistence of toxins in the treated larval habitats. This study monitored the impact of LLML FourStar® and LL3 on non-target organisms cohabiting with mosquito larvae in an operational study to control malaria vectors in western Kenya highlands. A total of 300 larval habitats were selected in three highland villages. The habitats were first monitored for 5 weeks to collect baseline data on non-target organisms cohabiting with mosquito larvae and then randomized into two treatment arms (respective FourStar® and LL3) and one control arm. Non-target organisms were sampled weekly for 5 months after treatment to assess the impact of LLML intervention. Before treatment, the mean density of all non-target organisms combined in the control, LL3 and FourStar® treated habitats was 1.42, 1.39 and 1.49 individuals per habitat per sampling occasion, respectively. Following treatment, this density remained fairly unchanged for 21 weeks at which time it was 1.82, 2.11, and 2.05 for the respective control, LL3 and FourStar® treated habitats. Statistical analysis revealed that LL3 and FourStar® did not significantly alter abundance, richness or diversity of the 11 taxa studied, when comparing the intervention and control larval habitats. However, both FourStar® and LL3 significantly reduced the density of malaria vectors. In conclusion, one round of label rate application of FourStar® or LL3 in natural larval habitats did not alter richness, abundance or diversity of the monitored aquatic non-target organisms cohabiting with mosquito larvae to an ecologically significant level.

Keywords: Bacillus sphaericus; Bacillus thuringiensis var. israelensis; aquatic vertebrates and invertebrates; larviciding.

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Figures

Figure 1
Figure 1
Location of study villages in Western Kenya Highlands
Figure 2
Figure 2
Study design
Figure 3
Figure 3
Abundance of individual taxa of non‐target organisms in treated and control mosquito larval habitats (a: insects; b: other organisms)
Figure 4
Figure 4
Impact of LLML on immature stages of mosquito. (a) Anopheles mosquitoes (Anopheles gambiae complex and An. funestus group) and (b) Other mosquito species combined
Figure 5
Figure 5
Diversity of non‐target organisms surveyed in different mosquito larval habitat types
See this image and copyright information in PMC

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