Evaluating wildflowers for use in conservation grass buffers to augment natural enemies in neighboring cornfields

Abstract

Adding wildflowers to arable lands is a tactic used to engineer agroecosystems to provide additional ecosystem services by attracting and supporting beneficial arthropods. Two studies were conducted to investigate the ability of wildflowers to influence populations of natural enemies. In the wildflower study, 24 early, mid and late season flowering species native to the USA Mid-Atlantic region were evaluated for their attractiveness to natural enemies and competitiveness with a perennial grass over two years. Insectary values were assigned to each wildflower based on length of flowering and relative attractiveness adjusted for background natural enemy activity. Wildflower species differed significantly in their ability to attract natural enemies, provide floral resources during the growing season, and maintain continued growth and flowering when contiguous with a perennial grass. Over two years, 45.9 to 82.4% of beneficials captured on sticky cards were hymenopteran parasitoids and their abundance was the major driver accounting for differences among wildflower species. At the farm level, we evaluated effects of wildflower addition to grass buffers on natural enemies in adjacent cornfields. Significant increases in taxa richness, abundance, and diversity of beneficial arthropod communities were measured in cornfields adjacent to grass buffers with wildflowers. Taken together, both studies provide evidence that insectary wildflowers can augment natural enemies in crop fields. However, differential attraction, flowering period and competitive abilities of wildflowers should be considered when selecting insectary species to mix with permanent grass buffers.