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Phenology Model Database

Smooth Crabgrass

Scientific name: Digitaria ischaemum

Phenology models predict timing of events in an organism's development. For many organisms which cannot internally regulate their own temperature, development is dependent on temperatures to which they are exposed in the environment.

Information in this database comes from published articles. It may be used in conjunction with field monitoring and a degree-day calculator.

Note: Before using a model that was not field tested in your location, you should test the model for one or more seasons under your conditions to verify that it will work for you.


Model 1 of 1

Fidanza, M.A., P.H. Dernoeden, and M. Zhang. 1996. Degree-days for predicting smooth crabgrass emergence in cool-season turfgrass. Crop Science 36: 990-996.

Location of study: Silver Spring, Maryland (field study)

Developmental threshold
Lower:53.6°F(12°C) soil temperature at 2.5 cm depth

Method of calculation: Max-Min Method: Degree-days = [(Tmax - Tmin)/2] - To, where Tmax is the daily max temperature, Tmin is the daily min temperature, To is the lower threshold. Set Degree-days to 0 when To > (Tmax - Tmin)/2.

Degree-day accumulations required for each stage of development

Biofix: April 1 in mid-Atlantic and Northern U.S.

 DD (°F)DD (°C)
First emergence76-14042-78
Initial major emergence252-414140-230
25% emergence558310
50% emergence801445
75% emergence1107615
95% emergence1701945

Could be used as guide for targeting post-emergence herbicide applications.


Statewide IPM Program, Agriculture and Natural Resources, University of California
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