Growing Degree Days "GDD"

Spring is here and you're trying to decide what the best plan of attack is for Poa-annua control on greens, Crabgrass, other undesirable weeds, & insects on the course. Over the years, you would hear from the old greens keepers that, if you watch for certain plants to bloom, then it's time to spray. Growing Degree Days (GGD) or the use of phenology as the method of predicting weed emergence has taken the guesswork out of when to apply.

How does this work? Growing degree day accumulation is the sum of the numbers of degrees by which each day's average temperature exceeds a base temperature. For most organisms, the base temperature is 50ºF. For example: if the average daily air temperature on March 12th was 58°F, the growing degree day (GDD) would be 8. Each day thereafter, the GDD numbers are added together to give a total accumulative GDD figure. Negative growing degree days are considered to be zero.

By monitoring weed emergence patterns in conjunction with calculating degree-days accumulation, turfgrass managers can develop a guide for targeting pre-emergence (residual) herbicide applications in their own region. It is important to understand that biological processes do not suddenly turn on when a specific degree-day total is reached but they occur within a range of degree days.

This may sound a little confusing, but the great thing is universities have been tracking this data for some time now and will be your best resource. I suggest that you contact your local university or extension office, who will be more than happy to assist you.

If anyone has other websites that I can share with everyone please let me know and I am not sure but I bet there is an APP for GGD also.
Email: Lsharp@tee-2-green.com

Resources:
www.ggdtracker.net
www.usbr.gov/pn/agrimet/gdd.html
www.nrcc.cornell.edu/grass/


Thanks Scott for sending the info for Cornell