Degree-day Accumulation - A degree-day is simply the average temperature for any given day. Degree-days are calculated by adding the high temperature (HT) and the low temperature (LT) for any given day and dividing the result by two (Fig. 1).
Often, the degree-day calculation is modified with a temperature threshold, called the Base. This temperature threshold is usually related to some significant temperature for the model. The base is simply subtracted from the degree-day calculation for the day. If subtracting the base results in a negative number, the degree-day calculation equals zero (Fig. 2).
Finally, degree-day accumulations are determined by simply summing the degree-day calculations over time. Often, degree-day accumulations will have a starting date based on some significant event in the model. This starting date for the ascospore maturity degree-day model is called the Biofix (Fig. 3).
