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Cold Weather and Fruit Development

Cold still grips North Jersey with 24F forecast tonight and 23F for Wednesday night followed by a slight warming trend.

The question is when will spring get here or rater when will green tip arrive on apple.

Reprinted from the Cornell Tree Fruit Grower Alert Message – Tuesday, April 2, 2013
by Mike Fargione- Cornells Hudson Valley Lab

Forecasting Apple Bud Break for the Mid Hudson Valley
By Terence Robinson, Mike Fargione and Steve Hoying

      Yesterday a grower in Hudson, Columbia County reported Manchurian crabapples began showing green tissue on Easter Sunday.  This cultivar typically starts to break bud at least a week before commercial cultivars.  Using forecasts for the next 2 weeks (until April 14) we have refined the previous green tip estimates for Highland, Ulster County to April 13 for early blooming varieties (Idared) and April 14 for mid bloom varieties (Delicious).  The weather forecast indicates we will slowly accumulate growing degree hours in the next few days and then rapidly accumulate growing degree hours beginning on April 4.
      We caution that the estimated dates of green tip are dependent on the accuracy of both the models (which in most cases is quite good) and the weather forecast (which is often not so good).  Our prediction of April 13 is 2 days earlier than we predicted last week due to slightly warmer forecasted temperatures in the next 2 weeks. Just in case, we suggest growers in the Highland area be ready to begin fungicide sprays to control scab by April 8.  Warmer parts of the region could be even earlier.

Editors Note- Ususally in Hunterdon County NJ we are 2-3 days behind the Hudson Valley timing projections, which could put us at green tip April 8-10- I would suggest you get your sprayers ready to go!

Forecasting Bud Break in the Spring of 2012
Terence Robinson, Mike Fargione and Steve Hoying

      The winter of 2012/2013 has been quite normal with numerous days in the fall and early winter with optimum temperatures for chill unit accumulation (32-60°F). Using the chill unit model developed in North Carolina which is an improved version of the original chill unit model from Utah we estimate that in the Hudson Valley, chill units began to be accumulated in late September (18th) and reached an accumulation of 1200 chill units on Jan. 12, 2013.  It should be noted that low chill varieties of stone fruits which require less than 1200 chill units completed rest even earlier than most varieties of apple.