Vegetational (living) and structural (non-living) complexity can influence arthropods in agricultural systems. In this thesis, both forms of complexity were manipulated in cabbage fields. In 2010 and 2011, a field experiment was conducted examining the effects of herbicide intensity and oat kill date on arthropods, weeds, and crop yield. Reduced herbicide intensity was associated with 1) lower abundance of several key cabbage pests and, 2) greater abundance of important natural enemy species. Habitats with both later oat kill dates or reduced herbicide intensity contained 1) fewer herbivores with chewing feeding guilds and more specialized diet breadths and, 2) greater abundance of active hunting natural enemies. In 2012, mulch species and mulch management practices were examined. Although mulching did not provide significant pest suppression, several generalist and one specialist parasitoid responded positively to habitat complexity. Predation and parasitism rates determined from natural enemy exclusion cages indicated no impact of mulching on the biocontrol of a major cabbage pest, the imported cabbageworm. In 2012, natural enemy behavior was observed in a y-tube olfactometer to determine the role of odor cues from decaying mulch on habitat choice. In general, natural enemies were not attracted or repelled by mulch odors. Further work is needed before implementation of these habitat management strategies (e.g. mulching and reduced weed management) and caution should be taken to avoid reducing cabbage yields or enhancing hyperparasitism.
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