HOST RELATIONSHIPS OF APHIDIUS TESTACEIPES (CRESSON) AND PRAON AGUTI (SMITH), PRIMARY PARASITES OF APHIDS

The host relationships of the braconid Aphidius testaceipes with the aphids Aphis gossypii and Myzus persicae, and those of another, Praon aguti, with the aphids Macrosiphum rosae and Macrosiphum pisi were ascertained. Another aphid host, Myzus circumflexus, was common to both.A. testaceipes preferred A. gossypii on squash to the aphid on hibiscus, and M. persicae on tobacco to that on radish. P. aguti did not show such plant host discrimination. Although A. testaceipes preferred M. persicae to A. gossypii, the latter was more suitable for successful parasitization, while M. rosae, the preferred host of P. aguti, was more suitable than M. pisi. During the extended absence of preferred hosts, the species indiscriminately attacked various stages of an unusual host, M. circumflexus, the number of attacks exceeding that on preferred hosts. Cases of successful parasitization were few, giving rise to abnormally small offspring incapable of effecting successful parasitization.The parasite species were very active on warm sunny days at temperature 29 °C and relative humidity 72%, and they performed the maximum number of strikes at 29 °C and 28 °C respectively. A decrease in the field population of A. testaceipes coincided with an abundance of the hyperparasite Asaphes fletcheri (Crawford).