Following a three-year study in commercial ‘Honeycrisp’ orchards, Rich Marini, Professor of Horticulture at Penn State University, and Tara Baugher, Penn State University Extension Educator in Tree Fruit, have developed a predication model for bitter pit.
The research team studied the relationship of bitter pit incidents and the measurement of minerals in fruit peels.
“Bitter pit was negatively correlated with calcium and consistently positively correlated with potassium, phosphorous and ratios of magnesium/calcium, potassium/calcium and nitrogen/calcium,” they write.
They also found bitter pit increased as shoot length increased and bitter pit decreased as crop load increased.
“The best combination of variables for predicting bitter pit was average shoot length plus the nitrogen/calcium ratio in the fruit peel,” they wrote.
The team posts a chart to help growers predict the potential for bitter pit based on shoot lengths on the Penn State University Tree Fruit website. Baugher and Marini say this model shows the need for good management of terminal shoot growth as well as management of calcium and nitrogen in the fruit.