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The UVM Apple Team

Dr. Lorraine Berkett,  Terence Bradshaw,  Sarah Kingsley-Richards, Morgan Cromwell

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The UVM Apple Program:

Extension and Research for the commercial tree fruit grower in Vermont and beyond...

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Vermont Apple IPM Focus

  L.P.Berkett, IPM Specialist

2008 Degree Day Accumulation for Plum Curculio Oviposition

Timing Insecticide Sprays using a Predictive Model


2008  Estimated Degree-Day Accumulation (Base 50F, from 95% McIntosh Petal Fall Date) for Selected Sites



South Burlington Chittenden Co. 

Elev. 71 M


Addison Co.

Elev. 107 M

South Hero

Grand Isle Co.

Elev. 54M


Windham Co.

Elev. 171 M

95% McIntosh Petal Fall Date

5/17 5/14 5/19 5/20


57 66 25 30


82 125 90 101


201 246 196 219


327 373 322 381

Date for 308 dd base 50 from 95% PF

6/14 6/10 6/14 6/12

Degree Day and other weather information received from Skybit E-Weather Service:

Beginning at petal fall, cumulative heat units are recorded using a base temperature of 50F. Daily heat units can be calculated as (Max+Min)/2-50 where Max and Min are maximum and minimum temperatures. If this quantity is less than zero, no heat units are accumulated. Daily heat units are summed beginning at petal fall and no further insecticide applications are required provided the last insecticide was applied no later than 10 to 14 days prior to the date when summed units reach 308. Note that thisdegree day threshold is different than the recommended value in the past.   Entomologists at Cornell have revised this value to reflect a correction in the metric to SAE conversions used (

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