With bloom being three to four weeks earlier than average this year, most tree-fruit crops are also being harvested earlier than usual. In a cherry trial that I have at the AREC, what few fruit survived the March 27 frost were harvested about three weeks ahead of last year. Likewise, we are picking peaches two to three weeks ahead of last year.
In our apple blocks, we are already seeing large fruit sizes for this time of year.
For apples, there are several prediction models that are used to estimate harvest dates. I used a model from Michigan State University that was published in HortTech by Randy Beaudry et al. (1993) to predict harvest maturity for apples.
The model predicts the first Red Delicious pick for Controlled Atmosphere (CA) storage, assuming that:
- For this pick the desired starch is between 2.5-4 and the firmness is between 17-18 pounds.
- There are 143 days between 80% full bloom and the first CA harvest
- Deviations from 143 days are based upon the minimum temperatures for the 15 days after 80% full bloom. For each degree Fahrenheit change from 50F there is a 1 day plus or minus change in the harvest date.
- For Winchester, using March 29 as the 80% full bloom date, the model is predicting August 27 as the date for the first CA harvest.
- For Batesville, using March 29 as the 80% full bloom date, the model is predicting August 25 as the date for the first CA harvest.
(As a side note, it is interesting that both Winchester and central VA called March 29 the full bloom date. I choose the date for Winchester, and a grower choose the date for central VA.)
While the model isn’t perfect, when I ran data from 2011 and looked at harvest maturity indices, it was remarkably close. The model predicted Sept 10 as the harvest date; on Sept 12, Reds were at starch = 4.2 (8-pt scale), Brix = 13, and firmness = 17.9 lbs.
Since most growers have at least a few Reds, harvest dates for other varieties can be approximated. Otherwise, a rule of thumb is “for each 2-3 days departure for the normal bloom date, there will be a one-day departure from the normal harvest date.” Blanpied and Silsby (1992).
While there might be other factors that affect these predicted dates, especially given the oddities of this year, growers should be advised about the potential for such an early harvest. Some things to consider with an early harvest: the availability of labor when the fruit is ready to be picked, PHI, seasonal maximum rates for pesticides, and when to start applying stop-drop materials. I’ll talk more about stop-drop strategies when we meet at Cline’s Orchard and Graves Mountain Lodge in July.
Please let me know if any questions arise about this model or the predicted dates. Or, for that matter, horticultural questions in general.
Best regards,
Greg
References
Beaudry, R., P. Schwallier, and M. Lennington. 1993. Apple Maturity Prediction: An Extension Tool to Aid Fruit Storage Decisions. HortTechnology 3(2): 233-239.
Blanpied, G.D. and K.J. Silsby. 1992. Predicting Harvest Date Windows for Apples. Information Bulletin 221: A Cornell Cooperative Extension Publication, Ithaca, NY.