| Abstract: | The fire ant, Solenopsis invicta Buren, was accidentally imported into the southern United States and has become a serious medical and agricultural pest of nine southeastern states and Puerto Rico. For a bait toxicant to be effective in fire ant control it must have delayed activity over a wide range of concentrations. Less than 1% of the 7500 compounds screened since 1958 has had delayed action. This paper describes several classes of fluorinated compounds that exhibit delayed activity. These compounds are used to illustrate the following three approaches to the discovery of delayed-action toxicants: (a) random screening of compounds for delayed action; (b) design of delayed activity through the synthesis of pro-insecticides; and (c) serendipity. As a result of these investigations two new classes of insecticides were discovered. A compound from one of these classes (tetrahydro-5,5-dimethyl-2(1H)-pyrimidinone (3-(4-(trifluoromethyl)phenyl)-1-(2-(4-(trifluoromethyl)phenyl)-ethynyl)-2-propenyl-idene) hydrazone, has been commercialised, while one or more compounds from the second new chemical class (fluorinated sulphonamides) are under development. Fluorinated delayed-action insecticides have made significant contributions to current fire ant control and will no doubt play a role in the future. |
