UW Extension Ag Weather

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Tree Pest Development

Tree Pest Development

Yesterday's Tree and Shrub Pest DD Map

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Development of tree and shrub pests can be estimated using a modified base 50 F degree-day calculation. For these pests the degree-day summation is started well before the growing season.

The map below represents the accumulation of degree days for any given location in Wisconsin. A degree day is a unit of heat for each degree above the base temperature in a 24 hour period. This map uses a base temperature of 50 degrees F and begins calculating degree days from January 1st of the current year. Locate your location on the map and see what color corresponds with that location. Then, find that color in the color bar below the map to determine how many degree days have accumulated for your location since January 1st.

Degree day accumulations can be used to determine distinct phenological events such as when specific plants will bloom, when to plant vegetables, and when insect pest outbreaks will occur.