Today's newsletter includes an update on degree day accumulations, mean temperatures, and precipitation. This newsletter also marks the start of the Honeycrisp fruit maturity assessments as an early check-in. Perennia will continue to track the rate of change in maturity indices leading up to harvest. In the meantime, remember to come to the grower meetup tonight and bring an appetite for homemade cookies. This brief newsletter is a supplement to the preharvest newsletter posted on August 13.
Table of Contents:
- Degree Day Accumulations
- Mean Temperatures and Precipitation
- Reducing bruising
- Considering watercore
- Avoiding internal browning
- Pesticide preharvest intervals
- NSFGA Grower Meet-Up
- NSFGA/Perennia Growing Good Growers Tailgate
Weather
Degree Day Accumulations
Degree day accumulations are warmer than average. Jeff Franklin shares that, "As of today, only the year 1999 has more base 5°C heat units than 2024". Harvest dates are difficult to predict based on degree day accumulations alone but it is very likely that harvest will be on the early side this year and should be monitored closely. Use harvest dates from 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 20 for the past 17 seasons. Provided by Jeff Franklin (AAFC).
- Approximately 6% more plant development heat units compared to the 5-year average, and 7% more compared to the 10-year average.
- Approximately 8% more plant development heat units compared to 2023, and 2% more compared with 2022.
- Approximately 8% more insect development heat units compared to the 5-year average, and 9% more compared to the 10-year average.
Mean Temperatures and Precipitation
Table 1 shows monthly temperature and precipitation totals for the growing season in comparison to the 25-year averages. This season is 1°C above the average so far. The increase in the average temperature relates to relatively warm nighttime temperatures. With the exception of the two large precipitation events in July, we have not been receiving very much rain.
Table 1. Mean monthly temperatures and precipitation totals for the current year compared with the 25-year averages. Provided by Jeff Franklin (AAFC).
Honeycrisp Fruit Maturity Report
- Similar to last year, Perennia will give short weekly updates as indicators of Honeycrisp and Ambrosia maturity.
- I started Honeycrisp assessments this week but I will be away next week, so reports will resume on the week of Sept 3.
- This is the earliest that I have taken maturity assessments so I do not have comparisons with prior years. However, I wanted to get a head start during this potentially early season to track the rate of change leading up to harvest.
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.
The maturity assessments from August 19 are summarized in Table 2 and Figure 2.
- The starch has not yet started to convert to sugars so all Honeycrisp fruit are at the highest starch rating of 1.0.
- The average DA value ranges from 1.0 to 1.2. We will track the rate of change over time but an early rough estimate would say that it would take about 4 weeks to reach the target value of 0.6 for harvest (at an average rate of -0.1 units per week).
- I am impressed by colour so far as it varies from 11-27% on the outer canopy (Figure 2). This colour development is likely related to recent cool nights of around 11°C and 13°C. Although the red colour may have an early start it is still early and temperatures in the coming weeks will 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.
Table 2: Maturity indices for regular Honeycrisp fruit sampled on August 19, 2024.
Figure 2: The blush red colour side of ten-fruit samples from three regions on August 19. Sampled fruit are from the outer canopy that would be targeted for a first pick. Subjective ratings estimate the red colour coverage at 11-27%.
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.
Harvest Fruit Quality
Reducing Bruising
Recommendations:
- Apples picked after significant rain will bruise more easily than if they’re picked when the soil has a lower moisture capacity. This information might be helpful for varieties especially sensitive to bruising.
- Let fruit warm up before harvesting. Apples picked in the cool weather of early morning bruise more easily than those picked in the day’s warmth. Generally, susceptibility to bruising decreases gradually from 0 to 15°C.
- Take the time to educate staff about the proper way to perform harvest activities that reduce bruising. For example, pick the bottom of the tree first, don’t overfill the picking bag, avoid long harnesses that let the bag bump against knees when walking, explain the difference between varieties etc.
- Re-grade orchard roads prior to harvest to lessen bumps that would jostle fruit being transported in bins.
- Have an inspector sample fruit from various positions in the bin two times each week and leave at room temperature for 24 hours to check for signs of bruise development.
- If bins of fruit will sit in the orchard during overnight freezing temperatures, place the bins where they will be shaded from direct morning sun. Direct sun will warm the fruit too quickly and can lead to deep and lasting bruises.
Considering Watercore
Watercore is a fruit disorder closely associated with over-mature apples along with several other factors. It happens most frequently in years with high sunshine and lack of cloudy, rainy days. Also, highly coloured and large fruit are most prone to the disorder. Fruit with the disorder have an appearance of water-soaked flesh because the spaces between the cells become concentrated with sugars instead of air. Small signs of watercore can disappear in storage and add sweetness to fruit. However, more serious watercore can reduce gas exchange in the fruit and lead to internal breakdown.Recommendations:
- Mature fruit are more likely to develop the disorder because as fruit mature the starches are converted to sugars. The sugar solution builds up in the fruit. Blocks that have a history of watercore should be harvested before other blocks.
- Consider products to delay harvest maturity. Both ReTain and Harvista labels state delayed onset and incidence of watercore.
Avoiding Internal Browning
Internal browning is likely related to carbon dioxide injury. The disorder frequently occurs in overmature and large fruit that have high carbon dioxide concentrations. In particular, fruit harvested late in the harvest window are most susceptible because as fruit mature their ability to diffuse internal carbon dioxide concentrations decreases. The internal carbon dioxide builds up and increases the chance of injury. Consider using products that delay harvest maturity.Pesticide Preharvest Intervals
There is now a product list containing all pesticides from the apple guide (without a schedule format). Here's how you can access the product list online:
- Visit the online pest guide tool at https://www.perennia.ca/pest-guides/
- Click on the tab for 'Tree and Vine Fruit Pest Guides' and choose either 'Insects, Diseases, and Growth Regulators' or 'Weeds'
- Under View Options select 'List of All Pesticides Contained in this Guide' or 'List of all Herbicides Contained in this Guide'
- In the table, the products are sorted alphabetically by default. Click on the column header 'Preharvest Interval, PHI (days)' once to sort by PHI in ascending order (short to long PHI) or click a second time to reverse the sorting direction to descending order (long to short PHI).
Events
NSFGA Grower Meet Up
Nova Scotia Fruit Growers' Association has organized an informal meet up, designed to bring growers together to chat, socialize, and get off the farm! Talk spray programs, summer plans, your favourite Olympic gold medalist, whatever you like! And come and find out if Michelle Cortens makes cookies that justify her time spent indulging in baking shows.
Where: Spurr Brothers Market, 14145 Evangeline Trail, Wilmot, NS B0P 1W0
When: Tuesday, August 20th, 2024
Time: 6:00pm
NSFGA/Perennia Growing Good Growers Tailgate
The Growing Good Growers tailgate session will be held at Stirlings Mountainside Farms 2017 on Thursday, August 22 @ 11am. The topic is preharvest management strategies such as ReTain and Harvista. Have you tried using ReTain or Harvista to delay or synchronize maturity or are you interested in trying it? What other advantages might there be for storage quality? Do you wonder if colour delay is a risk? What has been local experience with timings and products? Please bring your thoughts, experiences, and questions on preharvest management and join us for this discussion. Let’s continue the conversation from last year!
Please meet us in the orchard on the west side of Bains Road in Centreville (near civic address 100).
There is no need to RVSP, and we encourage you to bring your own coffee and snacks. Everyone is welcome to attend! It’s a good chance to catch up with friends.
This Orchard Outlook has been published with the input of the Orchard Outlook Committee including this week's contributors: Jeff Franklin, Bob Prange, and Danny Davison.
Perennia Food and Agriculture Corp.
Edited by Michelle Cortens, Tree Fruit Specialist
