Abstract:
Cotesia plutellae (Kurdjumov) (Hymcnoplera: Braconidae), is an effective parasitoid of Piute/la xylostella (L.) (Lcpidoptcra: Yponomcutidae :Plutellinae). Life history and level of parasitism of C. plutellale were investigated in relation to host-age under laboratory conditions in Jaffna, Sri Lanka. The study was conducted during April 2004 to May 2005 at mean temperature 25.6 ± 1.5 °C. Female C. plutellale oviposited• in all four instars of host larvae. The highest level of parasitism (99%), represented by the host preference was observed when newly emerged 3rd instar larvae were offered. The level of parasitism increased with the host age up to the 3rd instar and decreased with host age in the 4th instar. Total developmental period of the parasitoid was 12-15 days. The larval period was significantly shorter with the increasing host age but the pupal period was not significantly influenced. The mean adult longevity of the parasitoid population (N=30), developed on 3n1 instar host larva was (16 days) significantly longer than the longevity of the other group of individuals. Body length and wingspan of the adult parasitoids increased with lhe age host-age at initial parasitism. After egression, the host larva survived for nearly 24 hours wilhoul feeding
