Tuesday, April 11, 2017

Growing Degree Days

Plants and insects do not look at the calendar.  The "clock" that times their biological processes is often temperature related.

Growing Degree Days is an attempt to make that clock visible. 

Table from HERE  
The data shown above is from an MSU Integrated Pest Management site that is about fifteen miles east of Eaton Rapids.  If you look at the table shown above you can see that we had accumulated 379(base 42) growing degree days in 2012 but only 50 in 2013.

I wonder if the diagonal red streak starting in the southwest corner of the Lower Peninsula is an anomaly or if it is from the Chicago/Gary heat bubble.
Fruit growers use this data to time the application of pesticides.  They don't have to guess when plum curculio will emerge.  They have data.  That means they don't need to start spraying a week early to ensure their fruit is protected.

One quirk regarding Growing Degree Days is that it is calculated using a couple of different base temperatures.  For example, the site listed above makes them available using 32F, 40F, 42F and 50F.  The reason for the different base points is different organisms become biologically active at different temperatures.  Pussy willow, for instance, seem to become active at any temperature above 32F.  Many insects don't start clocking until the temperature is over 50F.  Fruit trees and their early development of flower buds seem to start at 42F.

1 comment:

  1. Heh! My first (and favorite) father-in-law had a favorite method for knowing when the ground was warm enough to plant.
    "Watch dem wimmen, fishing from the bank." He'd say, "When they sitting on the bucket, it's too cold to plant, but when they sit their butts on the ground, it's warm enough to plant."