In short-term, small-scale field experiments, population densities of two specialist herbivores differed significantly among different-sized patches of host plants. Eggs and larvae ofPieris rapae(L.) (Lepidoptera: Pieridae) were more abundant on collards planted in small (four- or nine-plant) patches than on those in large (64- or 81-plant) patches. Larvae ofplutella xylostella(L.) (Lepidoptera:Plutellidae) were more abundant on collards in large (81-plant) patches.