Does density of host plant (Asclepias syriaca) influence monarch butterfly (Danaus plexippus) oviposition?

Declining populations of monarch butterflies (Danaus plexippus) and their host plants has led to the establishment of the Iowa Monarch Conservation Consortium to support the implementation of a sustainable conservation plan for Iowa. One of the projects being conducted by Iowa State University members of the consortium focuses on whether preference and frequency of D. plexippus oviposition is influenced by the density of their host plants. The effects of plant density on oviposition preference were examined by monitoring monarch eggs on 2m² plots with 1, 5, or 10 plant groups of common milkweed (Asclepias syriaca).  A.syriaca plants were transplanted from the greenhouse into riparian buffer strips, prairie, and conservation reserve program lands across four farms in Story and Boone Counties, Iowa. Each plot of 1,5,or 10 plants was arranged 10m apart in an equilateral triangle with four replicates at least 100m apart at each farm. Preliminary results indicate that for all triangles (replicates) with at least one egg, oviposition preference appears to be for plants in higher density groups. If A. syriaca planted in higher densities appears to be preferred by D. plexippus for oviposition, planting single plants may be less effective as a monarch conservation strategy.