Mosquito Species Succession and Physicochemical Factors Affecting Their Abundance in Rice Fields in Mwea, Kenya

• Published in: Journal of medical entomology 2007-03, Vol.44 (2), p.336-344
• Main Authors: Muturi, Ephantus J., Mwangangi, Joseph, Shililu, Josephat, Muriu, Simon, Jacob, Benjamin, Kabiru, Ephantus, Gu, Weidong, Mbogo, Charles, Githure, John, Novak, Robert
• Format: Article
• Language: English
• Subjects: abiotic factors; agroecosystems; Animals; Biodiversity; Biological and medical sciences; Culicidae; Culicidae - classification; Culicidae - physiology; ecological succession; Ecosystem; Environment; environmental factors; Fundamental and applied biological sciences. Psychology; growing season; Kenya; Larva - physiology; larvae; larval habitat; Medically important nuisances and vectors, pests of stored products and materials: population survey and control; mosquitoes; Oryza - growth & development; Oryza sativa; physicochemical; physicochemical properties; Population Density; Population Dynamics; Regression Analysis; rice; rice cropping cycle; Seasons; species diversity; Statistics as Topic; succession; temporal variation; Time Factors; VECTOR-BORNE DISEASES, SURVEILLANCE, PREVENTION; Vectors. Intermediate hosts
• ISSN: 0022-2585; 1938-2928
• DOI: 10.1603/0022-2585%282007%2944%5B336%3AMSSAPF%5D2.0.CO%3B2

The succession of mosquito species and abiotic factors affecting their distribution and abundance in rice (Oryza spp.) fields was investigated over a 16-wk rice growing cycle covering the period between January and May 2006. Fifteen experimental rice plots were sampled for mosquito larvae and characterized based on rice height, number of tillers, floating vegetation cover, water depth, water temperature, turbidity, salinity, pH, dissolved oxygen, total dissolved solids, and conductivity. Microscopic identification of 3,025 larvae yielded nine mosquito species predominated by Anopheles arabiensis Patton (45.0%), Culex quinquefasciatus Say (35.8%), Anopheles pharoensis Theobald (9.0%) and Ficalbia splendens Theobald (7.1%). Other species, including Anopheles rufipes Gough, Anopheles coustani Laveran, Anonopheles maculipalpis Giles, Culex annulioris Theobald, and Culex poicilipes Theobald made up 3.1% of the total collection. Anopheles gambiae s.l., Cx. quinquefasciatus, and An. pharoensis occurred throughout the cycle, but they were more abundant up to 4 wk posttransplanting with peaks after fertilizer application. As rice plants became established, three groups of mosquitoes were recognized: the first groups included An. rufipes, Fl. splendens, and Cx. annulioris, which occurred throughout much of the second half of the rice cycle, whereas the second group included Cx. poicilipes, which was found in the middle of the rice cycle. An. coustani and An. maculipalpis formed the third group occurring toward the end of the cycle. Dissolved oxygen, number of tillers, and rice height were negatively associated with the abundance of An. arabiensis and Cx. quinquefasciatus larvae. In addition, Cx. quinquefasciatus also was associated with water depth (−ve) and turbidity (+ve). Abundance of An. pharoensis larvae was significantly associated with water temperature (+ve), the number of tillers (−ve), and rice height (−ve), whereas Fl. splendens was significantly associated with the number of tillers (+ve). The results demonstrate a complex nature of the interactions between some of the factors in the ecosystem and mosquito species abundance and calls for time-dependent and species-specific mosquito control operations.