Abstract
The instar preference and parasitization (expressed as mummification rate) of Aphis gossypii Glover and Myzus persicae (Sulzer) (Hemiptera: Aphididae) by the parasitoid Aphidius colemani Viereck (Hymenoptera: Aphidiidae) were studied at 25±0.5°C, 65±5% r.h. and a 16L : 8D photoperiod. The female parasitoids were 24-36 h old and were left to forage for 1 h on an eggplant leaf on which 10 nymphs of each instar of A. gossypii or M. persicae were placed. The percentage of A. gossypii nymphs mummified was higher than that of M. persicae (43.2 and 25.2%, respectively). The parasitoid parasitized nymphs of all instars of both aphid species, but it showed a preference for 1st and 2nd instars of A. gossypii and 1st instar of M. persicae. Nymphs of both aphid species parasitized in the 1st and 2nd instars were mummified when reached the 4th instar or adult stage, whereas those parasitized in the 3rd and 4th instars were mummified in the adult stage. The importance of these results in the effectiveness of A. colemani in biological control of A. gossypii and M. persicae is discussed.
Highlights
Aphidius colemani Viereck (Hymenoptera: Aphidiidae) is a polyphagous solitary endoparasitoid of aphids (Starý, 1975)
The parasitoid showed a higher mummification rate on A. gossypii than M. persicae (Table 1). This is consistent with the results of van Steenis (1993) who recorded a higher parasitization on A. gossypii (70–80%) than M. persicae (47–56%) by A. colemani reared on sweet pepper with M. persicae
A. colemani has been found to exhibit a preference for A. gossypii compared to M. persicae (Wellings et al, 1994; Messing & Rabasse, 1995)
Summary
Aphidius colemani Viereck (Hymenoptera: Aphidiidae) is a polyphagous solitary endoparasitoid of aphids (Starý, 1975). A. colemani was the most promising among four parasitoid species tested for biological control of M. persicae (van Steenis, 1995). This parasitoid is widely used in the biological control of A. gossypii in glasshouse crops (van Schelt et al, 1990; Grasswitz & Reese, 1998; Eilenberg et al, 2000) and against M. persicae on eggplants (Easwaramoorthy et al, 1976; Bolckmans & Tetteroo, 2002). Host instar selection by a parasitoid is among the most important factors that affect its potential to reduce an aphid population, since it affects both aphid and parasitoid population increase (Hågvar & Hofsvang, 1991). The quality of the host could affect the size, sex ratio, longevity and fecundity of the adult parasitoid (Hågvar & Hofsvang, 1991; Sequeira & Mackauer, 1992; Pandey & Singh, 1999)
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