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