Honeycrisp Fruit Maturity Report - Sept 21, and Storm Preparation

Wednesday, September 21, 2022

This update includes current degree day accumulations, an update on Honeycrisp maturity, and suggestions to prepare for possible high wind gusts this weekend. I'm crossing my fingers that we do not see damaging winds.

Update on 2022 Degree Day Accumulations

This year continues to be above-average for heat unit accumulation. Reportedly, harvest dates appear to be similar to or slightly earlier than they were last year.

Figure 1: Heating degree day accumulations for plant (above 5°C) and insect (above 10°C) development from March 1 to Sept 21 for the past 17 seasons. Provided by Jeff Franklin (AAFC).
  • Approximately 5% more plant development heat units compared to the 5-year average, and 4% more compared to the 10-year average.
  • Approximately equal plant development heat units compared to 2020, and 5% more compared with 2019.
  • Approximately 5% more insect development heat units compared to the 5-year average, and 4% more compared to the 10-year average.

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 where maturity is expected to be delayed.

Table 1: Maturity indices for Honeycrisp fruit sampled in Rockland on Sept 20 and in Lakeville and North Medford on Sept 21.

The average DA value for measured fruit in the regions is approaching the target of 0.60. DA values will be noticeably different between the most mature and least mature fruit on a tree and these ratings represent the overall average. Over the last week, starch conversion to sugars has progressed from last week's range of 1-2 to this week's range of 2-4 (Figure 2). Firmness has decreased by about 1 lb of pressure. Colour has noticeably increased (Figure 3).

Figure 2: The visual results of starch-iodine tests on a ten-fruit sample across all four locations being monitored. Average ratings are reported in Table 1. Sampled in Rockland on Sept 20 and in Lakeville and North Medford on Sept 21.

Figure 3: An example of the visual results of colour ratings on Sept 13 versus Sept 21 showing an increase in colour development over the past week.

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 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 both the red and green sides.

Firmness - Measured using a handheld penetrometer with a 7/16 inch diameter plunger on ten representative fruit.

Recommendations for Storm Preparation

Fire Blight

  • Have streptomycin available to treat nonbearing orchards within 24 hours of exhibiting damage to foliage or limbs. Note the preharvest interval before use on any bearing trees.
  • Streptomycin should not be used as a preventative treatment in the case of a tropical storm and should be saved for post-infection activity. If applied before trauma, streptomycin can be washed off leaves, degraded by sunlight, and will not provide protective activity if bacteria is moved in from outside the orchard.
  • Do not rely on Kasumin for a trauma event because this antibiotic is not systemic and will only kill cells on the surface of leaves and shoots. Meaning, any bacteria that moves into tissues will not be affected by Kasumin or copper.
  • Remember, bacteria can still be delivered to wounds in cool temperatures. Temperature matters for blossom blight risk because bacteria rely on heat to grow on the floral stigma. For trauma blight, the source of the bacteria is active infections that already have excessive bacterial populations contained in ooze. Trauma events are always cause for concern because bacteria are transported from active infections to open wounds.

Other Management

  • Before high winds, pick fruit from trees with a heavy crop load if possible especially if trellis systems are already exhibiting strain.
  • If applicable, contact crop insurance soon after you observe damage.

Blog Archive