Regeneration of silverleaf nightshade root segments from various depths.

Silverleaf nightshade (Solanum elaeagnifolium Cav.) is a widespread deep-rooted summer-growing perennial weed. It is considered amongst the worst weeds of cropping and pasture systems. The extensive root system of silverleaf nightshade competes both directly and indirectly with summer and winter pastures/crops, respectively, through depletion of soil moisture and other resources.Silverleaf nightshade is capable of forming new plants from both seeds and root segments. It is believed that cultivation is a major factor contributing to the spread of silverleaf nightshade. To determine the importance of cultivation in the spread of silverleaf nightshade, a glasshouse experiment investigated the response of various lengths of silverleaf nightshade root when buried at several depths. Reduced cultivation systems may decrease the spread of silverleaf nightshade. Results indicate that silverleaf nightshade can regenerate from root segments as short as 1 cm. Significantly more shoots are produced from 10 cm root segments at all depths compared to shorter root segments. No mortality was observed for 10 cm root segments, whereas mortality significantly increased as segment length decreased. However, despite the increased mortality of shorter segments, increasing fragment size did not reduce overall shoot density. These findings have implications for how a paddock infested with silverleaf nightshade should be managed. Minimum tillage techniques should be used when any sowing operations are undertaken. It would also be crucial that all implements are thoroughly cleaned prior to moving machinery out of an infested field, as even short root segments should be considered viable and therefore capable of starting a new infestation in a clean field.