Predicting Red Haven harvest date

Editor’s note: This article is from the archives of the MSU Crop Advisory Team Alerts. Check the label of any pesticide referenced to ensure your use is included.

A good prediction of peach harvest dates helps growers, shippers, marketers and buyers plan their season. For Michigan, the start of significant peach volume is with the harvest of Red Haven, and so a good predictor for this variety would be valuable to many.

To this end, I have collected dates for the onset of significant commercial Red Haven harvests in Berrien County since 1995 and have correlated this with various combinations of degree day models using weather data from the Southwest Michigan Research and Extension Center. The following is my first stab at a degree day model for Red Haven harvest onset. This is very preliminary, and it is unclear how to use these results in other locations, but these results should be of value until a better model is devised. (view image)

The Red Haven harvest onset model uses a degree day accumulation starting January 1 through June 3. Regression analysis was used to predict harvest onset. The resulting predictive equation is D = -0.0428x + 236.78, where x is the cumulative GDD50 from January 1 through June 3 and D = the day of year (e.g. January 1 = 1 and December 31 = 365 in a non leap year.

For 2006, the GDD50 through June 3 was 524. Plugging this into the formula, the estimated start of Red Haven harvest is 214.3, which is August 2. As can be seen, the trend line is not a perfect fit to the data. The observed harvest date is often three to five days from the predictor line. There are other factors such as temperatures after early June, rainfall and crop load that will affect peach maturity, and these factors are not considered in this current model. However, this model will provide a rough guide to the start of Red Haven season.

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