Behavior of Epidinocarsis diversicornis (Howard) and Acerophagus coccois Smith (Hymenoptera: Encyrtidae), parasitoids of two mealybugs of cassava, Phenacoccus herreni and Ph. Gossypii (Townsend & Cockerell) (Homoptera: Pseudococcidae)

Abstract

The parasitoids E. diversicornis and A. coccois have been found abundantly in Meta (Carimagua) and Valle del Cauca (CIAT-Palmira), respectively, attacking P. herreni and P. gossypii in cassava cultivar. In order to compare the behavior of the two Hymenoptera, the following situations were determined: develop­mental stage of P. herreni preferred by the aforementioned parasitoids, en­capsulation by the mealybug, mortality of P. herreni due to parasitism under laboratory conditions (25°C and 70% RH), effect of temperature (20°, 22°, 25° and 30°C) on the development of both natural enemies to estimate the physiological time or accumulative temperature, given in days-degree (°D), necessary to complete the development and minimum threshold of development. The result showed that the 3rd. nyn­phal instar and the adult female of the mealybug were the stages preferred by the parasitoids. Encapsulation by P. herreni was verified in E. diversicornis but not in A. coccois. P. gossypii did not produce encapsulation in either species of parasitoids. E. diversicornis caused mortality in the first instar of P. herreni, but A. coccois did not cause this kind of effect on the mealy­bug. The average period from oviposition to adult emergence was 35.7, 20.2 and 18.1 days for E. diversicornis and 39.5, 18.5 and 19.7 days for A. coc­cois at 20°, 25° and 30°C, respective­ly. A minimum threshold of 230°D for E. diversicornis and 175°D for A. coccois was found.