Effects of Intra- and Interpatch Host Density on Egg Parasitism by Three Species ofTrichogramma

Abstract

Host-foraging responses to different intra- and interpatch densities were used to assess three Trichogramma spp. (Hymenoptera: Trichogrammatidae) Trichogramma deion Pinto and Oatman, T. ostriniae Pang and Chen, and T. pretiosum Riley — as potential biological control agents for the Indian meal moth, Plodia interpunctella Hübner (Lepidoptera: Pyralidae). Single naïve females were allowed 6 h to forage in Plexiglas arenas with four different spatial arrangements of host eggs, nine single-egg patches), nine four-egg patches, 36 single-egg patches, and 36 four-egg patches. No significant differences were found among species in the number of patches parasitized. As expected, all three species parasitized the most eggs in the 36 four-egg patch treatment and the least in the nine single-egg patch treatment. T. deion parasitized significantly more eggs than T. pretiosum on the nine four-egg patches. T. ostriniae parasitized significantly more patches when intrapatch density was greater, regardless of interpatch density. In contrast, T. deion only parasitized more patches at the greater intrapatch density when the interpatch density was low. Patch density had no effect on T. pretiosum. The spatial pattern of parasitism was more aggregated for T. deion and T. ostriniae in the 36 four-egg patches treatment compared to the 36 single-egg patches treatment. Therefore, intrapatch density was more important than interpatch density for T. ostriniae, and potentially for T. deion, but not for T. pretiosum. T. deion may be the best candidate for augmentative biological control because it parasitized either slightly or significantly more eggs than the other two species in all four treatments. Furthermore, the pattern of parasitism by T. deion in the 36 four-egg patches treatment was the most aggregated among the three species, suggesting a more thorough searching pattern. In contrast, T. pretiosum had the least aggregated pattern of parasitism and therefore may have used a more random foraging pattern.

Assessing the Total Mortality Caused by Two Species of Trichogramma on Its Natural Host Plutella xylostella (L.) at Different Temperatures

“…To fully understand the impact of these other sources of mortality on pest regulation in the field, further studies should investigate the factors not addressed in this study that may affect mortality not directly related to parasitism, such as host age, host density (patch size), and the access to food resources by parasitoids, as these are all factors that may also affect host choice and the successful host parasitization by Trichogramma (Reznik & Umarova 1991, Makee 2005, Pratissoli et al 2009, Grieshop et al 2010.…”

Simulation of Scenarios of a Deep Population Crisis in a Rapidly Growing Population

“…A threshold that the population passes in a discrete model with a bifurcation following the outbreak does not arise in the pest, but arose in its natural enemies due to attacks by superparasites [72]. The specific parasitic efficiency of introduced wasps of the family Trichogrammatidae was found to increase with the increasing density of moth eggs [73].…”