Managing perennial summer weeds with competitive pastures

Prairie ground cherry (Physalis viscosa L.) and silverleaf nightshade (Solanum elaeagnifolium Cav.) were both introduced into Australia from central America in the early 20th century as contaminants of fodder and grain (Parsons and Cuthbertson 2001).Both these species are deep rooted, summer active perennials that utilise resources over summer, therefore competing directly with pastures and indirectly with the subsequent winter crops. Herbicides are relied upon as the primary method of controlling these weeds, although few land managers have reported successfully eradicating wide-spread infestations.Tideman (1960) reported that silverleaf nightshade did not appear to be greatly controlled by pastures containing either lucerne or phalaris. However, pastures are still worth consideration in an integrated weed management (IWM) program, as Wapshere (1988) reported that silverleaf nightshade densities declined over three years in fields returned to pasture after a cropping phase. Moerkerk and Snell (2003) have suggested that competitive perennial pastures are a control option for prairie ground cherry.This research aims to identify a range of summer pasture species that will suppress prairie ground cherry and silverleaf nightshade populations. Use of competitive pastures within an IWM program will have the benefits of increasing available summer pastures and decreasing reliance on herbicides for weed management.