Submitted to: Weed Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/21/2004
Publication Date: 3/1/2005
Citation: Masin, R., Zuin, M., Archer, D.W., Forcella, F., Zanin, G. 2005. WeedTurf: A predictive model to aid control of annual summer weeds in turf. Weed Science. 53:193-201. Interpretive Summary: Crabgrass and other weedy grasses are continual problems in turf. To be effective, the pre-emegrence herbicides that are used to control these weeds must be applied in a timely fashion. That is these herbicides must be applied immediately before the weedy grasses emerge. If applied too early, they degrade or volatilize, whereas if applied too late, the grass seedlings are too large to be affected. Consequently, a tool that makes use of site-specific weather variables to predict when weed grasses germinate and emerge in turf may be very useful. In this study the germination characteristics of four annual grass weeds (crabgrass, yellow foxtail, green foxtail and goosegrass) were investigated over a range of constant temperatures and water stresses. These were used to develop a computer model that allows users to predict the timing of seedling emergence based upon daily weather data. The model, called WeedTurf, predicted emergence with some accuracy, especially for large crabgrass, which is the most important turf weed in the central and northern United States and much of Europe. WeedTurf can be used to determine the critical times for application pre-emergence herbicides to control crabgrass, which should be beneficial to homeowners, sports turf managers, golf course managers, as well as crop consultants and the agri-chemical industry.
Technical Abstract: Predicting weed emergence is useful for planning weed management programs with limited herbicide use. Unfortunately, our ability to anticipate initial emergence and subsequent levels of emergence from simple field observations or weather reports are not good enough to achieve optimal control. Weed emergence models may provide predictive tools that help managers anticipate best management options and times and, thereby, improve weed control. In this study the germination characteristics of four annual grass weeds (crabgrass, yellow foxtail, green foxtail and goosegrass) were investigated over a range of constant temperatures and water stresses to calculate base temperatures and base water potentials. These parameters were used to develop a mathematical model describing seedling emergence processes in terms of hydrothermal time. Hydrothermal time describes seed germination response in a single equation by considering just the interaction of soil water potential and soil temperature. The model, called WeedTurf, predicted emergence with some accuracy, especially for large crabgrass and green foxtail. These results suggest the possibility of developing interactive computer software to determine the critical timing of weed removal and provide greatly improved recommendations for herbicide application timing.