Density of Anomoea flavokansiensis on Desmanthus illinoensis in monoculture and polyculture

The effect of plant species diversity on the density of the herbivore, Anomoea flavokansiensis Moldenke (Coleoptera: Chrysomelidae), on Desmanthus illinoensis (Michaux) MacMillan (Mimosaceae), a promising North American legume for exploring the principles of diverse, perennial grain agriculture was examined. From mid‐June to early August A. flavokansiensis feeds on young leaves and inflorescences of D. llinoensis. At high density, A. flavokansiensis potentially reduces seed yield and is thus an important consideration for long‐term stands that are to be grown without insecticides. The potential to manage this insect via intercropping its host species with other, non‐host perennial species by monitoring A. flavokansiensis density on D. illinoensis within experimental monocultures, two‐species mixtures with Tripsacum dactyloides , and three‐species mixtures with T. dactyloides and Leymus racemosus was examined. Insects were censused 2–3 times weekly from mid‐June to early August at two sites from 1991 to 1995. In the first three years, beetle density was generally low (<1 per plant), and did not differ among treatments. In the fourth year, however, beetle density peaked at 15 and 25 insects per plant at the two sites, and was highest within monoculture for most dates. In 1995, density was again low, but tended to remain higher in monoculture at one site. The results suggest that beetle density on D. illinoensis can be reduced in polyculture and may hold promise for the management of this insect herbivore within perennial grain polycultures.