Bracon hebetor Say

Bracon hebetor is the most common gregarious larval ecto-parasitoid widely distributed throughout the country. There appears to be two strains of the parasitoid, one attacking field pests and the other stored product pests. Among the hosts recorded are Corcyra cephalonica Stainton, Dichocrocis punctiferalis Guenee, Eublemma olivacea Walker, Hellula undalis (Fabricius), Ostriniaicius kashmirica (Moore), Helicoverpa armigera (Hübner) and Opisina arenosella (Walker). It is a widely distributed and important parasitoid of Opisina arenosella in Kerala. Parasitism is observed throughout the year, it ranged from 26 .2 to 26.7% during the peak period of Opisina arenosella infestation (February to June).

Bracon hebetor Say is reared at room temperature (24-33°C) and RH (32-95%). Pairs sorted out from freshly emerged brood are caged in specimen tubes (8 x 2.5 cm). Fifth instar caterpillars of Corcyra cephalonica or any other lepidopteran larvae of similar size are provided for oviposition and the parasitised larva removed daily from cage and maintained separately. The parasitoids are fed with undiluted honey provided as tiny droplets on wax-coated paper strips.

Bracon hebetor completes its total developmental period in 8.67±1.52 (7-12) days. The egg, larval and pupal period are completed in 1.25±0.44 (1-2), 3.05±0.68 (2-4) and 4.38±1.15 (3-7) days, respectively. The egg viability is 79.24% larval survival 71.52% and 63% adults emerge from the cocoons.

The females start laying eggs 2-5 days after emergence on partially paralised host caterpillars. The paralysed larvae (not receiving the eggs) died within 3-5 days. Female parasitoids feed on hosts haemolymph.

The eggs are laid singly or in groups of two to eight. A female is capable of laying 229 eggs (142 - 345) on 14-32 hosts caterpillars during its life span of 20-63 days, the daily average being 2-27 and laid maximum number of eggs during the first ten days of oviposition period. A single host larva supported the development of l0.6 (range 1-29) eggs and 8.4 (range 1- 25) larvae of the parasitoid.

The average preoviposition period is 3(2-5) days, oviposition period 37.7 (22-55) days and post oviposition period 4.4 (1-8) days. The fecund female live for 45 (20-63) days.

B. hebetor parasitised 2nd to 5th instar caterpillars of Opisina, 4th and 5th instar caterpillars are ideal stages for mass multiplication of the parasitoid as they produced progeny of both the sexes.

B. hebetor complete its developmental period on larvae of Corcyra cephalonica in 8.6 (7-10) days. Oviposition period lasts for 13 (5-22) days. The mean fecundity is 72 (13-148). Females live for 24 - 53 days. Egg viability is 92% and adult emergence 81 %. Male to female ratio is 5:1

B. hebetor could parasitise 65.9 per cent Opisina arenosella and 52.3 Corcyra cephalonica. The female lays 39 eggs per O. arenosella and 2.6 per C. cephalonica