Predicting first green in apples for west Michigan

Michigan State University Extension is predicting a slightly behind normal date to green tip in west Michigan apples for 2013.

Growing degree day totals for the general west Michigan area are running behind normal averages, but for this time of year (April), these extreme annual differences can change quickly. The table below shows 2013 degree day accumulations as well as the 2012 totals as a comparison.

2013 degree day accumulations through midnight, April 1, 2013

Weather station

Degree days base 32 from Jan. 1

Degree days base 40 from Jan. 1

Degree days base 42 from Jan. 1

Degree days base 45 from Jan. 1

Degree days base 50 from Jan. 1

Rainfall (in.) since Jan. 1

Belding

175

45

30

16

3

5.02

CHES

155

42

29

16

3

5.63

Fennville (TNRC)

202

52

36

19

5

5.39

Fremont

154

30

18

8

1

7.55

Hart

148

28

17

7

1

5.85

Hudsonville

201

51

35

19

5

5.08

Kent City

173

41

28

14

2

6.57

Ludington

150

28

17

8

2

6.35

Sparta

160

37

25

12

3

6.94

Average DD from Sparta historical date for Jan. 1 through midnight April 1

299

 

86

 

29

 

Comparative date of average at Sparta

March 9

 

March 2

 

Feb. 25

 

Days +/- average at Sparta

-23 days

 

-30 days

 

-35 days

 

2012 DD totals for Sparta through April 1 and days + average

713 (+30 days)

417

366 days (+39 days)

301

209 (+45 days)

 

Data from Enviro-weather

Looking ahead to the weather forecasts, Michigan State University Extension educator Amy Irish-Brown and I are predicting a slightly behind normal date to green tip. We use MacIntosh as a reference variety every year. MacIntosh first green is approximately 110 DD42, with a range of 90 to 130 DD42. The total for 2013 from the Sparta station as of midnight, April 1, is only at 25 DD42, so we are a little behind the average, but this can change quickly with a few warm days this early in the year. We usually get 2 or 3 degree days base 42 per day this time of year – in 2012 we were adding over 20 DD42 per day!

Using calendar dates, normal first green for MacIntosh or other mid-season varieties in the Grand Rapids, Mich., area is around April 11. For comparison, dates of first green on MacIntosh for recent years were:

  • 2012 = March 17
  • 2011 = April 12
  • 2010 = March 23
  • 2009 = April 12

Looking at the 30-day forecast, temperatures appear to be moving towards a more normal pattern – upper 50s to low 60s for daytime highs and mid-30s to low 40s for lows. Taking normal daily average degree day accumulations for base 42 and adding them up, it looks like we might reach the 110 DD42 mark by about April 21.

Predictions being what they are, it’s probably safer to state that we expect to be at least a week behind normal for first green on MacIntosh – that leaves some wiggle room to be inaccurate, or at least as inaccurate as predicting the weather.

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