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Growing Degree Days
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T. Michael Likins

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(804) 751-4401
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Chesterfield County Cooperative Extension
P. O. Box 146
Chesterfield, VA 23832

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Chesterfield County Cooperative Extension
9501 Lori Rd.
Chesterfield, VA 23832
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Cooperative Extension
Growing Degree Days

This information will be updated weekly from March through October to provide current data for use in making pest management decisions.

The accumulated Growing Degree Days are 3000.5 from August 7 – 12, 2018.

What is Growing Degree Days (GDD)? 

  • The GDD are a measure of heat accumulation used by horticulturists, gardeners, and farmers to predict plant and animal development rates. For Example
    • the date a flower will bloom,
    • an insect will emerge from dormancy or
    • a crop will reach maturity.
  • By monitoring the GDD on a daily or weekly basis it is possible to respond accordingly with timely controls.  

How is it calculated? 

  • Calculating GDD is determined by the difference between the daily average air temperature and the base temperature of 50 degrees F (10 degrees C)
  • You must first find the mean temperature for the day. The mean temperature is found by adding together the high and low temperature for the day and dividing by two.

Max Temperature + Minimum Temperature/2   minus  Base Temperature =  Daily GDD 

How to use this table? 

  • Using the table below the information will improve the timing of control measures by helping predict when common pest will appear in Chesterfield County.
  • The table below uses the minimum GDD , from past years, to show how it is helpful to monitor pests on a daily or weekly basis in order to predict the appearance and respond accordingly.   
PEST Minimum GDD
Eastern Tent Caterpillar 92
Pine Tip Moth 121
Pine Spittlebug 148
Azalea Lace Bug 239
Two-spotted Spider Mite 363
Euonymus Scale 406
Boxwood Leaf Miner 448
Bagworm 600
Fall Webworm 867
Japanese Beetle 970


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