Downy Brome (Bromus tectorum) is a common weed species in a varieties of regions. The Downy Brome growing degree day model developed by researchers, uses heat units and time as a method to estimate plant phenological stages through the growing season. This can be helpful to predict plant emergence and to time herbicide applications before flowering occurs.

Calculating Growing Degree Days

For this model, a lower temperature threshold of 32F is used to calculate growing degree day accumulation. For the Northern Hemisphere, January 1st, should be used as a biofix, the date when to start growing degree day accumulation. Growing degree days can be calculated from daily high and low temperatures, or via the Pest Prophet app, which uses hourly temperature data for a given field. The first emergence will occur at 1440 GDD (F) with viable production at 1800 GDD (F).

Learn More:

Ball, et al. Predicting timing of downy brome (Bromus tectorum) seed production using growing degree days.Weed Science 52, July–August 2004Weed Science, 52:518–524. 2004