Weather summaries are included in this week's update along with some discussion points from the Orchard Outlook Committee. We continue to monitor and report on Honeycrisp maturity from the example regions. Maturity updates are meant to indicate the rate of change of ripening each week and, when possible, will be compared to past years.
It is our hope that you keep your spirits up through this tough time. Don't beat yourself up about decisions that are easy to critisize in hindsight. Everyone is affected by the ongoing drought and your care and concern for each other is admirable. Onward and upward, crew!
Total degree day accumulations are similar to the 5-year average and slightly warmer than the 10-year average (Figure 1). Harvest dates are difficult to predict based on degree day accumulations alone. Currently there is no evidence to suggest that harvest this year will be as early as it was last year in 2024. However, it's likely that harvest will be on the early side and should be monitored closely. Use harvest dates from similarly early years as estimates and leave a comfortable buffer for preharvest intervals with fungicides and insecticides.
Figure 1: Heating degree day accumulations for plant (above 5°C) and insect (above 10°C) development from March 1 to August 29 for the past 17 seasons. Provided by Jeff Franklin (AAFC).
Mean Temperatures and Precipitation
Figure 2 shows monthly temperature and precipitation totals for the current growing season in comparison with the 25-year averages. Temperatures have been cycling with a combination of above- and below-average temperatures. The net effect over July and August was near-average heat accumulation. However, heat waves throughout the summer brought extreme heat (>30°C) on 11 days compared with the usual 9 days.
Figure 2: Mean monthly temperatures and precipitation totals for the current year compared with the 25-year averages. Provided by Jeff Franklin (AAFC).
In terms of precipitation, we're not sharing anything you don't already know. The rain has been sparse with June at 51% of average, July 38% of average, and August at 15% of average according to Kentville data (Table 1). The dry weather has been a plant stressor and when combined with the additional extreme heat it has taken a toll.
Table 1. Precipitation totals (mm) by month for Kentville for the current growing season compared with the 10- and 25-year averages. Provided by Jeff Franklin (AAFC).
Honeycrisp Fruit 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 2, 2025 in Rockland and North Medford, and Sept 3, 2025 in Lakeville. Values are compared with the samples taken two weeks ago on August 18 & 19, 2025.
Please note that a new site has been selected for monitoring in Rockland and it will be used going forward. It is now in the block located on "The Flat" (contact me if you want specifics).
Table 2 Discussion:
- There are very early signs of starch beginning to convert to sugars in Rockland and Lakeville.
- Starch conversion is too early to give harvest predictions.
- The Orchard Outlook Committee discussed that starch staining this year is less intensely black than usual. We suggest that the relatively low intensity may be related to less total starch rather than starch conversion. When monitoring starch for maturity estimates, pay attention to the pattern of the stain rather than the overall intensity.
- The average DA value currently ranges from 0.98 to 1.27 depending on the site.
- So far the DA values are similar to what is expected during an average year.
- So far, the DA meter values suggest that fruit maturity is not as far advanced this year as it was last year. Last year was a very early year.
- This year rely on all maturity indicators due to the unfamiliar weather conditions.
- Even if DA values do not make sense for comparing years, the values should still be useful for comparing blocks to decide which to harvest first.
- Soluble solids values in our region for Honeycrisp tend to be 11% at harvest maturity but it depends on many factors including crop load. This year, without the diluting effect of water the soluble solids are already much higher than usual.
More observations (data not shown):
- There is less red colour development at this time than there was at this same time last year.
- Honeycrisp fruit on trees with deep root systems and limited drought stress weighed 176 g and measured 76 mm (3.0") in diameter. Fruit on young trees with drought stress weighed 127 g and measured 67 mm (2.6") in diameter. Fruit size will vary by crop load and soil moisture, but this information is shared for your general knowledge.
- Old trees or varieties grafted onto rootstocks with deep roots are producing the largest fruit sizes.
- Ethylene is reportedly showing up earlier than usual in drought stressed fruit. We do not have the answers but we wonder if ReTain may not work be effective in cases where the ethylene production has already begun. We do not yet know the influence of ReTain and Harvista on fruit quality when used during a drought but I hope to have more insight from another growing region soon.
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.
Using Iodine Solution for Maturity Testing
For those of you doing your own iodine testing please note:
- Generic iodine chart created for McIntosh is used as guidance.
- Consult your packinghouse for suggested starch index values used to determine the first acceptable harvest date of specific apple varieties.
- Local research by John Delong et al. 2013 and 2016 showed that optimal values for long-term storage are as follows: Honeycrisp between index 5.0 and 7.5 and Ambrosia between index 2.8 and 5.0
- The correct starch-iodine index numbers for the first acceptable harvest date will vary depending on region so be careful of numbers that you use from other regions. Typically more northern regions such as ours will have relatively higher starch index values than southern apple growing regions for the first acceptable harvest date because low temperatures preceding harvest favour the conversion of starch to sugar.
- Charts for varieties are available online but please note that the generic chart is the industry standard. The variety-specific charts just tend to show the variety-specific pattern of starch staining better than the figures developed using McIntosh. Just be cautious of the index values they report for long-term storage.
Perennia Food and Agriculture Corp.
Edited by Michelle Cortens, Tree Fruit Specialist
Edited by Michelle Cortens, Tree Fruit Specialist
