Recognition of parasitic hymenoptera of aphids in cotton, citrus and some vegetable crops in Valle del Cauca

Abstract

This study consisted of a taxonomic identifi­cation of parasitoids of aphids, a pest of great importance in several crops. Special reference was made to the parasitoids of the cotton aphid, in which observations were made on the per­centage of parasitism and habits under labora­tory and field conditions. Thirteen sites in the department of Valle were visited. At these sites, 21 crops were screened by taking samples of aphids. Field observations of the parasitoids of the cotton aphid were made at the farm «La Esmeralda», en Palmira. In vitro, observations were carried out in the laboratory of the Ento­mology Department of the Universidad Nacio­nal de Colombia in Palmira. Taxonomists de­termined the following parasitoids: Lysiphle­bus testaceipes (Braconidae) on Toxoptera aurantii; Diaeretiella rapae (Braconidae) on Macrosiphum euphorbiae; Lysiphlebus sp. (Braconidae) on Aphis illinoisensis and A. gossypii; Aphelinus sp. (Aphelinídae) on A. gossypii. Macrosiphum euphorbiae and an aphid on Asclepias curassavica. They also de­termined the hyperparasitoid Pachyneuron sp. (Pteromalidae), which was found on these bra­conids. The average percentage of parasitism of Lysiphlebus sp. was 44.15% and that of Aphelinus sp., 55.64%. Aphelinus sp., besides being a parasitoid, also showed predatory behavior, achieving an average control (parasit­ism + predation) of 71%. The length of life of Lysiphlebus sp.from oviposition to emergence was 9.73 days, with the longevity of 4.15 days for males and 5.41 days for females. For Aphelinus sp., these values were: 12.19, 11, and 19.77 days, respectively. Both species present parthenogenesis of the arrhenotoky type. and they prefer also aphids in the first to third nymphal instar at the time of parasitism. The two species showed differences in their habits of oviposition and the aphids attacked by these parasitoids showed a different appearance. Aphelinus sp. is never parasitoid and predator on the same individual. Under field condi­tions, the percent of parasitism was 2,2% by Aphelinus sp. and 0.3% by Lyziphiebus sp.