Orchard Outlook Newsletter Vol. 23, No 16 & Maturity Update

Tuesday, September 19, 2023

Today's newsletter includes an update on degree day accumulations, mean temperatures, and precipitation from Jeff Franklin (AAFC). Following hurricane Lee, I provide an industry update to connect you with what others have experienced in the industry including an overall sense of relief. There is some loss of fruit, trees, and trellis and the extent of bruising is unclear at this time. Also included is the second update on Honeycrisp fruit maturity that is nearing harvest maturity.

Table of Contents:

  • 2023 Degree Day Accumulations
  • Precipitation


2023 Degree Day Accumulations

The cumulative degree days for the entire season are essentially equal to the 5- and 10-year averages for base 5°C heat units (Figure 1). Industry members are reporting that fruit maturity is lagging a couple of days behind harvest dates in recent years.

Figure 1: Heating degree day accumulations for plant (above 5°C) and insect (above 10°C) development from March 1 to Sept 18 for the past 17 seasons. Provided by Jeff Franklin (AAFC).
  • Approximately equal plant development heat units compared to the 5-year average, and 1% more compared with the 10-year average.
  • Approximately 3% less plant development heat units compared to 2022, and 3% less compared with 2021.
  • Approximately 1% more insect development heat units compared to the 5-year average, and 2% more compared to the 10-year average.

    Mean Temperatures

    Fruit colouring has been a challenge. Likely the slow colouring is related to the warm temperatures that we have experienced so far in September. Jeff Franklin explains, "Currently, mean daily temperatures are running 2.8 °C ahead of the 25-year average and the average minimum temperatures are approximately 4°C ahead of the historical values."

    Table 1. Mean temperatures for the first 18 days of September, current year (2023), 10-year, and 25-year averages. Provided by Jeff Franklin (AAFC).


    The precipitation total for the growing season has now even exceeded the very wet year of 2019 (Figure 1). The surplus of water has happened from July onward. This is a good time to take note of wet areas in the orchard to see if areas prone to standing water also correlate with specific areas of poor tree health. Surprisingly, soil temperatures are above-average. 
    Figure 2: Precipitation recorded in Kentville for the 2023 season (red line) compared with the 10-year average (black line). Provided by Jeff Franklin (AAFC).

    Storm Update


    • Wind gusts appeared highest near the Minas Basin, Windsor, and on the South Mountain. However, wind gusts throughout the Valley were relatively similar in the range of 70-84 km/hr.
    • Estimates of fruit drop are lower than expected and are lower than recent events of Dorian and Fiona. Ambrosia is one of the worst-affected varieties with it's long and brittle stem. The extent of the cut and bruised fruit is to be determined.
    • There is occasional tree loss. Also, part or full rows of trellis with high density trees have collapsed where crop loads were heavy, post spacing was greater than 25 ft, or there was a knot in the centre of the end post. Failure has happened within blocks or on the eastern side.
    • Leaves are tattered and could have allowed entry of fire blight bacteria, especially during an already high-risk year. 

    Honeycrisp Fruit Maturity Report

    Table 2: Maturity indices for regular Honeycrisp fruit sampled in the current year on Sept 18, 2023 (Rockland)/Sept 19, 2023 (Lakeville and North Medford) and compared with last year's samples from Sept 20 (Rockland)/ Sept 21, 2022 (Lakeville and North Medford). The rate of change since last week's measurement is shown in brackets beside the current measurement.

    The average starch values for Honeycrisp fruit measured in all regions has not reached the target of 5. Maturity continues to be delayed relative to last year. Maturity values are becoming more noticeably different between the most mature and least mature fruit on a tree, distinguishing the first pick from later picks. 

    The average DA value for Honeycrisp fruit measured in all regions has not reached the target of 0.60 but is progressing as expected by losing about 0.1 units each week. 

    Please note that the use of the DA meter on fruit treated with ReTain has not been verified. The DA meter reading on the treated fruit is 0.69 suggesting near-maturity however the starch index values suggest otherwise. Starch index is a more reliable indicator in this case.

    Figure 1: Ten-fruit samples across all four locations. The ground colour (left) on the sampled fruit. The visual results of starch-iodine tests on Sept 12 (middle) and the change toward more sugars on Sept 18/19 (right). Starch ratings are reported in Table 1.

    Important Note - This maturity report 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 where maturity is expected to be delayed and is most likely targeted for a second pick timing.

    About each 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 handheld 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. 

    Other Notes

    Ambassadors for Temporary Foreign Worker Program

    An article in The Grower on September 13 brings to light recent criticisms of the Temporary Foreign Worker Program. As everyone who works within the program is an ambassador of it, this article is being shared here to bring it to your attention. The workers through this program are an essential part of the local industry.

    This Orchard Outlook has been published with the input of the Orchard Outlook Committee including this week's contributors: Larry Lutz, Joan Hebb, Kari Brown, Jeff Franklin, Bob Prange, Dustin MacLean and Heather Rand.

    Perennia Food and Agriculture Corp.
    Edited by Michelle Cortens, Tree Fruit Specialist

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