2019 ASHS Annual Conference

All major apple varieties can develop preharvest and post-harvest disorders, which make them not marketable or lower their value drastically. The apple cv. Honeycrisp is especially susceptible to several pre and post-harvest disorders, but due to its high value, this apple is one of the top varieties planted in Washington State in the first two decades of this century. A major problem in Honeycrisp cultivation is that the fruit is prone to bitter pit, which is a physiological disorder characterized by dark and sunken spots on the apple surface. This disorder starts in the orchard, but symptoms may appear before harvest or during storage. High numbers of marketable fruit are lost every year to this particular damage. This indicates a need for an easy and inexpensive test that would allow producers to have a reliable indication of potential storage losses due to bitter pit. A total of four bitter pit prediction methods were evaluated between 2016 and 2018: Passive, ethephon (also known as Bangerth), hot water and PennState method. The hot water and PennState methods were evaluated for two consecutive years only. The number of orchards evaluated yearly ranged from three to five depending on the year. Before collecting the samples, the amount of bitter pit in the field was assessed for each orchard. Symptom free Honeycrisp apples were harvested a few days prior to first commercial harvest from the west or south side of the tree. The fruit was transferred to a laboratory where the protocol for each method was followed. A sub-sample of untreated symptom free apples was stored in commercial cold storage for up to 12 weeks. The development of bitter pit on apples in storage was compared to the prediction values resulting from each bitter pit prediction method. In general, there was a lot of variability between orchards and years, and none of the methods have demonstrated accurate prediction of potential storage loss due to bitter pit incidence across the years. It is important to take in consideration, that none of the methods above mentioned account for in field losses, which are the apples that present symptoms in the orchard and are not harvested. Nonetheless, overall the ethephon and PennState methods had a better prediction rate than the passive and hot water method.