Parasitismo de Plutella xylostella (L.) (Lepidoptera : Plutellidae) por Oomyzus sokolowskii (Kurdjumov) (Hymenoptera : Eulophidae)

Abstract

Parasitoid dispersion and host location can be affected by abiotic and biotic factors related to the parasitoid and its host. Therefore, we investigated the effects of age, photoperiod, and parasitism of Oomyzus sokolowskii (Kurdjumov) (Hymenoptera: Eulophidae) under different densities of Plutella xylostella (L.) (Lepidoptera: Plutellidae), in the laboratory, green house and field. Moreover, we investigated the effect of superparasitism on O. sokolowskii fitness, its dispersion ability in the field, and the effect of a multiple host plant systems on its parasitism capacity. Results showed that there was no effect of the light regime (light or darkness) on the parasitization; although parasitoid was more active after 3h of light exposure. Female parasitization activity was maintained up to the age of 20 days, but the offspring emerged per host decreased as wasps aged. Parasitism rate increased with parasitoid age up to 96 h and when wasps received a constant number of hosts daily in comparison with a random number (13.3 versus 8.9 larvae). In addition, the number of larvae parasitized increased with host density, varying from 1.7 to 10.4, in the laboratory, and from 0.61 to 7.0, in the field. In the green house,parasitism was higher in microparcels with higher host infestation, and with more exposition time to parasitization (24h: 52.4% and; 72h: 80.7%). Regarding the superparasitism, it increased thenumber and longevity of offspring produced per larva, but decreased offspring body size. However, developmental time and sex ratio of parasitoid offspring were not affected. Parasitoids were able to disperse and parasitize larvae at similar rates throughout the field up to 24m from the releasing point. Intercropping of cabbage with broccoli, Napa cabbage, cilantro and green onion did not negatively affect parasitism rates of O. sokolowskii. Then, results suggest that O. sokolowskii could be favored by superparasitism and have the potential to control P. xylostella under different densities, regardless of the cropping system.