Low Temperature Effect on Viability of Diadegma insulare (Hymenoptera: Ichneumonidae) Pupae and Effect of This Parasitoid on Feeding Rate of Diamondback Moth Larvae (Lepidoptera: Plutellidae)

Abstract

Laboratory tests with Diadegma insulare (Cresson), a parasitoid of the diamondback moth (Plutella xylostella (L.)), were conducted to evaluate the viability of cocoons stored at 4°C for varying lengths of time and also the effects of parasitism by D. insulare on the feeding rate of diamondback moth larvae. The percentage of adults emerging from cocoons declined steadily with time spent in storage at 4°C and was predictable (r2=0.9603; Y=98.3-2.06X; P<0.01). No emergence of D. insulare was observed after 49 d in storage. There was a significant difference in feeding rate of parasitized larvae and non-parasitized larvae. Consumption of collard foliage by parasitized larvae (86.25% of them were parasitized) the first day after stinging was about the same as for non-parasitized larvae; but the parasitized larvae then became sluggish and fed very little on days 2-5 when the experiment was terminated.