Chemosterilization of Culex pipiens fatigans Wiedemann by exposure of aquatic stages. 2. Sterilization potential of certain phosphoramides and s-triazines.

Many aziridinyl compounds are known to induce high sterility in Culex pipiens fatigans Wiedemann, but as the practical application of these chemosterilants is quite hazardous, compounds such as phosphoramides and s-triazines have been tried against this species. These compounds are relatively less reactive, thermally more stable and less toxic to mammals. The phosphoramides included hempa, N,N,N',N'-tetramethyl-P-piperidino-phosphonic diamide (ENT-51007) and a compound, ENT-60210, whose structure is not known to the authors. The s-triazines employed were hemel, 2,4-diamino-6-morpholino-s-triazine hydrochloride (ENT-51143), 2-amino-4,6-bis (dimethylamino)-s-triazine hydrochloride (ENT-51146), and a compound ENT-60433, whose structure is not known to the authors.The triazines were more toxic than the phosphoramides in both larval and pupal treatments. Among the phosphoramides, hempa and ENT-51007 were quite promising for larval treatment and resulted in 80% and 83% control of reproduction respectively at non-toxic doses. Hempa at a toxic dose induced complete sterility. ENT-60210 was least toxic and least effective. Among the triazines, hexa-substituted hemel was better than tetra-substituted ENT-51146 and cyclic-substituted ENT-51143 in inducing sterility. ENT-51143 was most toxic and least effective. For larval treatment, hempa was better than hemel in inducing sterility while for pupal treatment the latter was better than hempa. Both the compounds produced more sterility in treated females than in treated males. Oviposition was significantly lowered in treated females.