Harvest time is approaching….

Terence Bradshaw

With these peak days of summer quickly moving by, it will soon be time to prepare for this season's harvest.  One problem virtually every grower encounters is determining the optimum time to begin harvesting their fruit for peak freshness.  All too often it seems that color is the primary factor determining harvest date, but this can get growers into trouble.  Last year we encountered a situation where growers waited for color to develop even as fruit quality was declining on the tree.  Unfortunately this "coloring period" coincided with the arrival of Hurricane Floyd and tremendous damage was done to last year's crop as a consequence.  While we may not encounter such a weather event every year, it is imperative to harvest fruit at a time where they will maintain their quality throughout the marketing chain. The easiest way to do this is with regular starch index (SI) testing.
We will be offering iodine solutions to growers again this year for use in SI testing.

It is recommended to test fruit once or twice weekly beginning three to four weeks prior to anticipated harvest.  Sampled trees should be representative of the orchard block in terms of crop load and tree vigor.  The representative sample should include at least ten fruit with no more than two fruit collected from the same tree.  Collected fruit should then be cut in half along the equator and iodine solution applied to them either by placing the fruit face down in a solution-filled pan or by spraying with a "Windex"-type sprayer.  After one minute, the stained fruit should be compared to a standard Cornell SI chart and values averaged to come up with an SI value for the fruit in that particular block.  This value can then be tracked and fruit harvested when the SI value indicate optimum maturity. As a general rule of thumb fruit with SI readings of 3-4 are suitable for late CA, apples measuring an SI value of 4-6 are best for early CA, and any fruit reading 6 or above should be placed in regular cold storage or marketed immediately.  These values are all relative and should be considered with other factors including but not limited to fruit drop and color, labor management, storage capabilities, and grower experience with particular blocks or varieties.

This year we came up with estimated harvest dates for McIntosh fruit for the South Burlington and Shoreham areas based upon the Cornell model for predicting apple harvest windows.  The formula we used is specific to the Champlain Valley and is dependent upon bloom date and mean temperature for the period thirty days after full bloom.  Temperature data was collected from Skybitâ weather services.

The results of this formula predict a late harvest this year, but growers should stay on top of their situation by regularly checking the fruit in their blocks and harvesting when necessary to maintain fruit quality.
Information for this article was based in part on Cornell Cooperative Extension Publications Information Bulletin 221 "Predicting Harvest Date Windows for Apples," by G.D. Blanpied and Kenneth J. Silsby.  We have copies of this publication available to growers on a first-come, first -served basis for $5.50.  We will also be offering bottles of iodine solution for SI testing at no cost again this year. Any interested growers can contact me at tbradsha@zoo.uvm.edu or 802-656-0490.