Host suitability of different instars of the whitefly Bemisia tabaci 'biotype Q' for Eretmocerus mundus
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Eretmocerus mundus Mercet is a parasitoid of Bemisia tabaci (Genn.) indigenous to the Mediterranean and is used commercially for augmentative biological control in Spain and elsewhere. A better understanding of the suitability of different host instars would help optimize production and field application. Incidence of parasitism, development time, survivorship and sex ratio were evaluated when different nymphal instars of the sweetpotato whitefly Bemisia tabaci biotype 'Q' were offered for parasitization. Experiments were conducted on sweet pepper at 25°C, 75% RH and 16:8 (L:D) photoperiod. E. mundus oviposited in all nymphal instars of B. tabaci except the mature 4th instar or pharate adult (previously designated, 'pupa'). Incidence of parasitism was greatest (33.8 ± 5.1 parasitized nymphs) and development time shortest (14.1 ± 0.1 d) when oviposition occurred under 2nd and 3rd instar nymphs compared to 1st or 4th instars. Survivorship (85%) and offspring sex ratio (39.8% female) did not differ statistically for parasitoids developing in whiteflies that were parasitized as different instars. Although 2nd and 3rd instars were clearly the most favorable host stage for E. mundus, its capacity to parasitize and develop on a wide range of host stages is a favorable characteristic for both rearing and field application.