DDT water emulsion in rice fields as a method of controlling larvae of Anopheles quadrimaculatus and other mosquitoes
Knowles, F.L.; Fisk, F.W.
Public Health Reports 60(35): 1005-1019
ISSN/ISBN: 0033-3549 DOI: 10.2307/4585363
A method of applying a DDT water emulsion at the pump to flooding waters of a rice field is described. Data obtained from 28,000 dipping records of larval counts are given according to DDT dosage, solvent used, and position of plot. The toxicity of the DDT-treated water decreased with the distance from the pump, so that sampling stations near the pump gave low larval counts, and the larval count increased with distance from the pump. In comparison with an untreated rice field, 2 plots of the treated field contained 50% fewer A. quadrimaculatus larvae and 72% fewer culicine larvae than the untreated field. In the l/20th-acre plots, complete control of anopheline and culicine larvae was obtained at DDT concs. of 1 ppm. and 0.2 ppm. respectively. Samples of rice stools from treated and untreated fields showed approx. 50% fewer rice weevil larvae in the treated than in the untreated field. Yields of harvested rice in the DDT-treated 100-acre field were higher than the average or highest yields for previous yrs., from untreated fields, and indicate that DDT did not injure the growing rice. Although these results indicate a reduction of mosquito larvae production by the application of DDT to the flooding water as it enters the rice fields, this production of mosquito larvae was by no means eliminated.