The maturity updates continue this week for Honeycrisp from the example regions. This information is meant to indicate the rate of change of ripening each week and, when possible, will be compared to past years. Also, please note the information about acquiring iodine solution.
Does your Farm Require Iodine Solution for Maturity Testing?
Contact Michelle Cortens to get your name on a list for distribution of iodine solution when it becomes available. Those of you who signed up during the tailgate meeting are on the early bird list and will be contacted as soon as the materials are ready.
Honeycrisp Maturity Report
Important Note - The following information is for general industry purposes only. Growers are encouraged to use their own discretion to harvest trees that are exhibiting delayed colour development or exhibiting maturity indices that disagree with what is being reported here. Values were measured on an average of fruit that were representative of the block's crop load and tree vigour. Fruit representative of size and colour were taken from all sides but not from the interior of the canopy where maturity is expected to be delayed and is most likely targeted for a second pick timing.
Table 2: Maturity indices for regular Honeycrisp fruit sampled in the current year on Sept 3, 2024 and compared with the samples taken two weeks prior on August 19, 2024.
Discussion:
- The starch has not yet visibly started to convert to sugars so all Honeycrisp fruit are at the highest starch content at a rating of 1.0.
- The average DA value is currently around 0.85 for fruit not treated with ReTain. I will continue to monitor the rate of change but an early rough estimate would say that it would take about 2.5 weeks from now (Sept 20) to reach the target value of 0.6 for harvest (at an average rate of loss of 0.1 units per week). However, in the past during years of above-average heat we have noted that the DA meter can be misaligned with other maturity indices so stay tuned for when starch degradation begins.
- Red colour continues to progress well for being early in the season. Red colour is averaging around 40% in the outer canopy that would be targeted for a first pick. The good colour is owing to recent weather when several cool nights were followed by warm and sunny days.
- Anthocyanin is the pigment responsible for red colour in apples. The process of anthocyanin formation begins when the precursors develop at temperatures below 15°C (or 21°C in the case of McIntosh) and then they are converted to anthocyanins at temperatures around 20-25°C during sunlight hours.
- Although the red colour may have an early start it is still early in the harvest season and temperatures in the coming weeks will continue to impact colouration. Strategies for colour enhancement should go ahead as planned.
- If you feel that fruit size is ahead of normal at this point, consider more bins in your bin estimate.
About each maturity measurement:
Starch Index - Starch is converted to sugars as ripening progresses. The starch-iodine test is used because iodine binds to starch molecules turning them blue/black, whereas sugars are not stained and remain clear. The Cornell chart on a scale of 1 to 8 was used above and values are an average of ten representative samples from each block.
Soluble Solids - Approximates the percentage of sugar content of the fruit. Measured using a digital refractometer. Values are an average of ten representative samples from each block.
DA Meter - The delta absorbance (DA) value is related to the chlorophyll content of the peel. AAFC researchers in Kentville developed a protocol for Honeycrisp. Values above 0.60 are immature, values 0.6 to 0.36 are ideal for long term storage, and values below 0.35 are best for short term storage because they are more prone to storage disorders. Values shown above are the average of twenty fruit taken throughout a block, with readings taken on the transition area between the sun and shade exposed sides. DA values will be noticeably different between the most mature and least mature fruit on a tree.
This Orchard Outlook has been published with the input of the Orchard Outlook Committee including this week's contributors: Danny Davison, Harrison Wright, Suzanne Blatt, Joan Hebb, and Bob Prange.
Perennia Food and Agriculture Corp.
Edited by Michelle Cortens, Tree Fruit Specialist
