congresos y reuniones científicas
Does host protection from mortality lead to high irreplaceable mortality from parasitoids? An example with wheat stem sawfly (Cephus cinctus Norton)
PETERSON, R.K; BUTELER, M.; D. K. WEAVER
Conferencia; Annual Meeting of the Entomological Society of America; 2009
In studies, researchers have suggested that insects herbivores in protected environments have higher mortality from specific factors than herbivores in non-protected situations, although overall mortalities in protected environments are often lower. However, to our knowledge this has never been examined using life table approaches. The primary objective of this study was to characterize the mortality dynamics of the summer larvae. The specific objectives were to (1) process samples to identify living and dead larvae and assign mortality factors, (2) construct multiple decrement life tables, and (3) analyze the life tables to estimate distributions and risks of mortality. Here, we specifically address irreplaceable mortality from the identified factors. In many temperate cropping systems, parasitism has a low irreplaceable mortality, which may explain considerable variability in efficacy with biological control, especially with free-living feeders (exophages). However, because wheat stem sawfly is protected within the stem during the entire larval developmental period (endophage), parasitism seems to be crucial to reducing numbers of larvae for this pest. This study supports the hypothesis that endophage insect herbivores experience fewer mortality factors than exophages and that the mortality factors are largely irreplaceable. From a practical perspective, manipulation of parasitism for endophage pests through augmentative releases may be beneficial because of the high levels of irreplaceable mortality from this factor.