Can plantings of partridge pea (Chamaecrista fasciculata) enhance beneficial arthropod communities in neighboring soybeans?

Grass buffer strips are often deployed along crop borders as part of conservation programs to improve water quality, filter sediments from runoff, and foster wildlife biodiversity. Addition of wildflowers in these strips can augment natural enemies by provisioning nectar and pollen resources. Here we investigated the impact of partridge pea [Chamaecrista fasciculata (Michx.) Greene] as an insectary plant to enhance natural enemy abundance in adjacent soybeans. In 2005, sticky card counts of hymenopteran and dipteran parasitoids were 72.7% higher in buffers of partridge pea and partridge pea mixed with purple tansy (Phacelia tanacetifolia Benth.) compared to purple tansy grown alone or proso millet (Panicum miliaceum L.), whereas predator abundance was greater in purple tansy and millet compared to buffers with partridge pea. Similarly, communities of beneficial arthropods captured in 2006 by sticky card and pitfall traps were 79.8-72.3% higher, respectively, in partridge pea buffers compared to neighboring soybeans. Buffer effects on populations of parasitoids and predators in adjoining soybean fields were mixed and varied among taxon groups. Partridge pea was a source for dipteran parasitoids and saprovores, but density effects were generally not discernible beyond 6 m within the adjoining soybean. More significantly, partridge pea acted as a natural enemy sink for mymarid parasitoids, dipteran predators, and ground-dwelling ants, and had a neutral effect on other arthropod guilds. Implications of these findings are discussed.