TVA has used DDT extensively as a larvicide since 1945 and to a lesser extent as an adulticide during the period 1945–1950. It is still effective for use as a larvicide for control of A. quadrimaculatus on TVA lakes. Its use as a residual spray has been discontinued, and its effectiveness for this purpose is now highly questionable.
In the TVA control program, chemical control measures have always been considered as supplementary, principal reliance being placed on environmental or naturalistic control methods. However, insecticides have been invaluable in the development of the program. They have served well pending the establishment of satisfactory environmental controls. There is a continuing need for efficient larvicidal measures for use when emergency situations arise and as a part of the regular control program to obtain the maximum benefit from water level management schedules. All control measures are frequently subjected to critical evaluation as to their economy and effectiveness under current conditions and changes made as might be indicated. DDT larvicidal measures are under close scrutiny at present because of the possibility of development of resistance. Concurrently, investigations of new insecticidal materials are underway so that a satisfactory substitute for the DDT larvicide will be available if needed.