Impact of floral herbivory by parsnip webworm (Oecophoridae: Depressaria pastinacella Duponchel) on pollination and fitness of wild parsnip (Apiaceae: Pastinaca sativa L)

Herbivory by the parsnip webworm, Depressaria pastinacella (Lepidoptera: Oecophoridae), on the flowers of wild parsnip, Pastinaca sativa (Apiaceae), has been shown to decrease the plant's reproductive success. This pilot study provides evidence that this reduction in fitness extends beyond physical removal of reproductive structures. Umbels infested with a single webworm were visited by potential pollinators less frequently and produced fewer (but heavier) seeds than uninfested umbels. While much of the reduction in seed production can be attributed to consumption of flowers by webworms, this study suggests that reduced rates of pollination also contribute to reduced seed set. Reduced pollination may result from decreased rates of pollinator visitation due to alteration of chemical orientation cues used by pollinators and by decreased pollinator access to flowers due to the presence of silken webbing.