EFFECT OF SOME ENVIRONMENTAL FACTORS AND AGRICULTURAL PRACTICES ON ABUNDANCE OF MOSQUITO SPECIES IN RICE FIELDS SOUTH EASTERN AL- KUT CITY

Abstract

The influence of environmental factors and agricultural practices on abundance of some mosquito species were studied in the rice fields southeastern Al-Kut City during the period ( 12/7 to12/11/2010) . Rice fields were sampled every two weeks to examine the relationships among water pH ,water temperature ,plant height ,turbidity ,water level, TDS and water conductivity with the number of larvae of each mosquito species. A total (108) larvae of four species belonging to two genera were identified : Anopheles, pulcherrimus Theobald , A. stephensi Liston, Culex pusillus Macquart, and C. theileri Theobald.The ratio of mosquito species as follow: genus Anopheles :.A. pulcherrimus 37.03% and A. stephensi 17.5% .genus Culex :C. pusillus 27% and C. theileri 11.1%. There were a significant positive relationship between two species of Culex while the relationship of both species were negative with A. stephensi . There were a postive significant relationship between both species of Anopheles,and versus that there were negative with C. theileri .The study showed that the large number (0.06) larvae/dip from species C. theileri was collected on (2-6) weeks when rice fields on (Young,Tiller and Mature phases),while the large number (0.23,0.3) larvae /dip from species C. pusillus was collected on the(3-4) weeks when rice field on Tiller phase .In other hand the large number from Anopheles species: A. .pulcherrimus and A. stephensi (0.56 ,0.43) larvae/dip respectively were collected in the eighth week when the rice field in the preharvest phase . This study showed that some ecological factors such as(water temperature ,water pH) more effective on the distribution and abundance of mosquito species especially C.theileri ,while plant height had negative effect on this species . Water turbidity was more effect on C. pusillus , while the TDS and water conductivity were more negative effective on A.stephensi and A.pulcherrimus respectively in the rice field.