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How to Manage Pests

Degree-Days: Additional Information

References

Baskerville, G. L. and P. Emin. 1969. Rapid Estimation of Heat Accumulation from Maximum and Minimum Temperatures. Ecology 50(3):514-517.

Andrewartha, H. G. and L. C. Birch. 1973. The History of Insect Ecology. In History of Entomology, ed. R. F. Smith, T. E. Mittler and C. N. Smith, 229-266. Annual Reviews Inc., Palo Alto, CA.

Allen, J. C. 1976. A Modified Sine Wave Method for Calculating Degree-Days. Environmental Entomology. 5(3):388-396.

Wilson, L. T. and W. W. Barnett. 1983. Degree-Days: An Aid in Crop and Pest Management. California Agriculture. 37:4-7.

Zalom, F. G., P. B. Goodell, L. T. Wilson, W. W. Barnett, and W. J. Bentley. 1983. Degree-Days: The Calculation and Use of Heat Units in Pest Management. University of California Division of Agriculture and Natural Resources Leaflet 21373.

Glossary

biofix:
the date when you begin accumulating degree-days, usually associated with a biological event.
degree-day:
a unit combining time and temperature, used to measure the development of an organism from one point to another in its life cycle.
double sine:
one method of simulating a temperature curve for a 24-hour period. Two sine curves are fit to the minimum and maximum temperatures for a day and the minimum temperature for the next day. Degree-day calculations are based on the area under the curve and between the threshold(s).
double triangle:
one method of simulating a temperature curve for a 24-hour period. Two triangles are fit to the minimum and maximum temperatures for a day and the minimum temperature for the next day. Degree-day calculations are based on the area under the curve and between the threshold(s).
horizontal cutoff:
a modification, in relation to the upper threshold, to the degree-day calculation method. A horizontal cutoff assumes that development continues at a constant rate at temperatures above the upper threshold.
Huber's:
a method for calculating degree-days that reduces the total degree-day accumulation if the minimum and maximum temperatures for the day are between the upper and lower thresholds.
intermediate cutoff:
a modification, in relation to the upper threshold, to the degree-day calculation method. An intermediate cutoff assumes that development slows as temperatures increase above the upper threshold.
lower threshold:
the temperature below which development stops.
single sine:
one method of simulating a temperature curve for a 24-hour period. A sine curve is fitted to the minimum and maximum temperatures for a day, in the assumption that temperatures are symmetrical around the maximum temperature. Degree-day calculations are based on the area under the curve and between the threshold(s).
single triangle:
one method of simulating a temperature curve for a 24-hour period. One triangle is fitted to the minimum and maximum temperatures for a day, in the assumption that temperatures are symmetrical around the maximum temperature. Degree-day calculations are based on the area under the curve and between the thresholds.
threshold:
(Physiological) the point at which a stimulus is just strong enough to be perceived or to produce a response.
upper threshold:
the temperature above which the rate of growth or development begins to decrease or stop as determined by the cutoff method.
vertical cutoff:
a modification, in relation to the upper threshold, to the degree-day calculation method. A vertical cutoff assumes that development does not occur at temperatures above the upper threshold.

Detailed figures and formulas

Degree-day routines


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