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Starch-index in tested McIntosh fruit rose by approximately one point from last week. Color continues to improve in McIntosh, with most growers able to do a first picking based on color in well-pruned or dwarf trees. Marshall McIntosh is already exhibiting pre-harvest drop in some orchards, while other strains are showing no or very minimal (push-off) pre-harvest drop. Fall-like weather should improve color and slow maturity somewhat, therefore, the real start the McIntosh harvest will begin later this week and continue into next week. Remember, the last date for CA harvested fruit at the UMass Horticultural Research Center in Belchertown is predicted to be September 22 based on bloom date and average temperatures 30 days following bloom. Plan accordingly.
Gala and Honeycrisp are not ready for harvest based on the starch test, however, growers are advised to keep a close eye on Gala for background color change from green to yellow.
Starch-Index Readings for 9/5/00
Deerfield: Marshall McIntosh 5.2; McIntosh 4.8; Redcort 1.0
Shelburne: Pioneer Mac 3.8; Honeycrisp 1.2; Gala 2.0; McIntosh
3.6
Colrain: McIntosh 3.7
Hawley: McIntosh 2.8; Honeycrisp 1.0
Note that all starch-index readings based on the Cornell 'generic' starch chart. Harvests of McIntosh fruit for CA should begin at a reading of approximately 4, rather than 3 as with the McIntosh chart used in the past. CA harvests should be complete when the fruit have reached approximately 6. Also, note that McIntosh starch levels are low on average, resulting in higher index values than the level of maturity suggests. Other varieties seem to have normal starch levels, so starch-iodine tests may be more useful for these.
Healthy Fruit is written by Dan Cooley, Ron Prokopy, Jon Clements, Starker Wright, Arthur Tuttle, Wes Autio, Bill Coli, and Duane Greene except where other contributors are noted. Publication is funded in part by the UMass Extension Agroecology Program, grower subscriptions, and the University of Massachusetts IPM Program. A text version can be e-mailed to you if you contact Doreen York. Please cite this source if reprinting information.
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