Many insecticides will kill the spotted alfalfa aphid—Therioaphis maculata (Buckton)—but even the most effective chemicals provide only a temporary relief from aphid attack. In most infested areas chemical control of the aphid is essential for successful alfalfa production. Furthermore, chemical control will continue to be essential until highly promising research on resistant alfalfa varieties— adapted to California growing conditions—can be completed or until fungus diseases or imported beneficial insects provide a more permanent control. Unchecked, this aphid can hamper alfalfa production, reduce the yield, and impair the quality of alfalfa hay, but it can be controlled economically by the careful use of chemical treatments that are properly applied.

The above progress report is based on Research Projects Nos. 1330 and 1443.