Effect of Compost Composition on the Abundance and Diversity of Generalist Insect Predators in Agricultural Fields

Agricultural fields can be difficult environments for recruiting and retaining natural enemies that may be effective for pest control. Detrital inputs can support natural enemies, resulting in a trophic cascade by encouraging the abundance of detritivorous prey. However, there has been very little consideration on the quality and composition of detritus, and how it may influence detritally-driven food webs. We examined how six compost treatments that were similar in carbon to nitrogen ratio but differed in lignin content would affect the abundance and diversity of generalist predators in broccoli fields. The six different treatments were: manure silage, hay, softwood, and hardwood and two controls including rice hulls and bare ground. Sampling occurred every two weeks from late June to late July using wet pitfall traps. We sorted, enumerated, and identified all samples to family and predatory insects to morph-species. Data from these samples were used to evaluate the effects of the different treatments on the abundance and diversity of generalist predators.