Abstract
Methods were developed to determine the efficacy of low dosages of petroleum derivatives against mosquito larvae and pupae. The type of test container, application technique, and quality of test specimens were evaluated. A comparison was made of the biological activity against 3 species with certain petroleum hydrocarbons as both freshly applied (1 gal/acre) and residual surface films (2 gal/acre), and applied to the larval siphon (0.25 μliter). The speed of entry of the test materials into the tracheal system and the surfacing habits of the larvae with respect to treated and untreated surfaces also were compared. In general, the order of susceptibility of the larval stages was Aedes taeniorhynchus Weidemann > Culex pipiens quinquefasciatus (Say) > Aedes aegypti (L.). However, the final mortality was virtually complete in all 3 species. The susceptibility of pupae to surface applications of ½ gal per acre ranged from 98% in C. p. quinquefasciatus to 100% in the other 2 species. The WHO/M/18 method was the most practical and desirable one for routine comparisons of efficacy of petroleum-derived materials. Species varied in their response to such agents and the response was closely related to the surfacing habits of the larvae. Because of the hypoxia mechanism involved, periods longer than 24 hours were needed to evaluate larvicidal effectiveness, particularly to obtain the final or ultimate effect and to isolate structures which provided a slow response (days rather than hours).
Published Version
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