Annual ryegrass control affected by choice of management system

Summary Annual ryegrass is the most challenging weed of winter crop production through its ability to evolve herbicide resistance to most chemical modes of action. This ability to adapt to changes in management regimes means that no one control measure is likely to effect control for any length of time.In order to understand this phenomenon better an experiment was undertaken at Wagga Wagga, NSW first to evaluate the relative importance of cultural and chemical control options in the absence of a competing crop. The treatments were then imposed for ryegrass control within a wheat system.Whereas, in the absence of a crop, pre-plant cultivation was significant in controlling ryegrass, the effect was not significant when a crop was present. Pre-emergent herbicides were more effective when a crop was present, with the competition from the crop suppressing later germination flushes. In all cases the combination of pre and post-emergents was the most effective.This project demonstrated that the study of weed biology in the absence of a crop may compromise the application of outcomes when put into practice in a crop.