Establishment of Imported Parasites of the Spotted Alfalfa Aphid In Arizona

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Abstract
About 235,000 pupae and adults of Aphelinus semflavus Howard, Praon palitans Muesebeck, and Trioxys utilis Muesebeck were shipped to Arizona between November 1955 and July 1957 for release in alfalfa fields infested with the spotted alfalfa aphid (Therioaphis maculata (Buckton)). Releases were made at several sites, the number at a single site ranging from 250 to more than 56,000. A. semiflavus has been recovered in small numbers at several locations in central Arizona, the last recovery being in April 1959 about 100 miles north of the nearest release site. P. palitans has been recovered several times in central and southwestern Arizona. In 1959 it was collected from five locations in the south-central and two in the north-central part of the State, but was of no consequence in control of the spotted alfalfa aphid. T. utilis is generally established in the alfalfa-growing districts of southern Arizona and is a substantial factor in controlling the aphid.