Host suitability of different instars of the whitefly Bemisia tabaci `biotype Q' for Eretmocerus mundus

Eretmocerus mundus Mercet is a parasitoidof Bemisia tabaci (Genn.) indigenous tothe Mediterranean and is used commercially foraugmentative biological control in Spain andelsewhere. A better understanding of thesuitability of different host instars wouldhelp optimize production and field application.Incidence of parasitism, development time,survivorship and sex ratio were evaluated whendifferent nymphal instars of the sweetpotatowhitefly Bemisia tabaci biotype `Q' wereoffered for parasitization. Experiments wereconducted on sweet pepper at 25 °C, 75%RH and 16:8 (L:D) photoperiod. E. mundusoviposited in all nymphal instars of B.tabaci except the mature 4th instar orpharate adult (previously designated, `pupa').Incidence of parasitism was greatest (33.8± 5.1 parasitized nymphs) and developmenttime shortest (14.1 ± 0.1 d) whenoviposition occurred under 2nd and3rd instar nymphs compared to 1st or4th instars. Survivorship (85%) andoffspring sex ratio (39.8% female) did notdiffer statistically for parasitoids developingin whiteflies that were parasitized asdifferent instars. Although 2nd and3rd instars were clearly the mostfavorable host stage for E. mundus, itscapacity to parasitize and develop on a widerange of host stages is a favorablecharacteristic for both rearing and fieldapplication.