Manipulation of Ground Predator Populations Affects Prey Removal in a Highbush Blueberry (Vaccinium corimbosum) Field
Zontek, Erica Lynn
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Arthropod predators such as carabid beetles (Coleoptera: Carabidae) can be effective natural enemies of pests in agroecosystems. In this experiment, the ground arthropod community in a highbush blueberry field (Vaccinium corimbosum) was manipulated to study the effects of predator abundance on prey removal. Different boundary types were established around plots to allow unidirectional movement of ground arthropods. Ingress boundaries permitted movement into plots, egress boundaries permitted movement out of plots and an unbounded control was used to assess naturally occurring populations. By measuring ground arthropod activity/density using pitfall traps within bounded plots, a significant effect of boundary type on the arthropod community was observed. Activity/density was highest in the ingress boundary plots, intermediate in the control plots and lowest in the egress boundary plots. Field predation experiments were used to assess the effect of ground arthropod abundance within each treated row by providing a fixed number of onion fly pupae (Delia antiqua). Boundary type had a significant effect on number of pupae recovered. Mean number of pupae recovered was greatest in the egress boundary plots, intermediate in the control plots and lowest in the ingress boundary plots. Regression analyses suggest that the mean number of pupae recovered decreased as a function of both carabid as well as other ground predator abundance. Laboratory feeding experiments showed that Pterostichus spp., one of the carabids collected in the field, did consume onion fly pupae. Further research focusing on convenient means to increase populations of carabid beetles and other arthropod predators may enhance pest management strategies in blueberries.