Production and pest update brought to you by the OMAFA Apple Team: 

Erika DeBrouwer, Tree Fruit Specialist and Kristy Grigg-McGuffin, IPM Specialist

The time of year we have all been working towards. Apple harvest is underway in most regions for early timed cultivars! Yay! Most regions have gotten a sprinkle of rain (thankfully!) over the past week. Cool nights have also been in the forecast as of late, where most growers are hoping for these trends to continue. Wishing you all the best over the harvest season!

Growth Stages

Fruit continues to size with colour developing the closer we get to harvest timing.

At the Simcoe Research Station, fruitlets and terminals are sitting at the following:

	Honeycrisp	Ambrosia	Gala
Fruitlet Size	82.2 mm	67.0 mm	66.3 mm
Terminal Growth	29.5 cm	26.9 cm	36.2 cm

Harvest Homework

There are a few ways to tell how mature your fruit is, which can take some trial and error in the field. These tools can be used to aid in planning your harvest logistics and should be used in a complimentary fashion with each other.

Starch

Starch testing is one of the most common maturity indictors due to ease and cost. Starch is an effective tool to use in the field as it provides a great visual and numerical ripeness representation of sugar conversion. Ultimately, the less stain that is shown, the more mature the apple is.

For more details, see Cornell Starch Iodine Index Chart

There are two recipes that can be used to perform the starch iodine test which are outlined below.

Test	Benefits	Challenges
Potassium iodide	– Good representative of sugar accumulation – Can be performed in the field or in a lab setting	– The recipe needs to be prepared by a pharmacist, chemist or veterinarian. – Iodine solution needs to be made fresh. – Solution is poisonous. – Can be difficult to perform in orchard.
2% iodine solution	– Good representative of sugar accumulation – More convenient regarding supplies than potassium iodide test – Can be performed in the field or in a lab setting	– Is more costly than recipe above. – Iodine must be diluted. – Can be difficult to perform in orchard.

Firmness

Firmness can be determine with handheld or tabletop penetrometers. This is also a common test that is easier to perform in the field than other tests. A handheld penetrometer gives you more flexibility and ability to test in the orchard.

Sugar

Sugar is another common indicator to determine ripeness, which is best utilized in tandem with acidity testing. Refractometers are used to determine the level of °brix within the fruit juice itself, with optical refractometers being the most typical. Remember to clean and dry off the instrument between each sample.

Sugar content is usually higher with reduced moisture, high temperatures and high sunlight.

Trees with high crop loads tend to have lower sugar levels.

Acidity

Acidity is commonly tested for in cider and wine-making, where levels decrease as fruit becomes more mature. Acidity testing can be performed with pre-made kits where the level of malic acid is shown. This test can be performed in the field but should be trialed over time.

Colour

Colour can be difficult to determine in the field when aiming for a precise level, especially with lighting changing throughout the day in the orchard. Luckily, for Ambrosia, a colour chart was developed by British Columbia to aid in determining harvest maturity based on the background colour of the fruit.

Ethylene

Internal ethylene can be measured using a delta absorbance (DA) meter. This is a less common test, as there are substantial difference in values across regions – but – it can be used throughout harvest if you are willing to spend time to develop a standard within the cultivar you are looking at.

Ripe on Cue

Cultivars vary in respect to ideal maturity for harvest. Below is a table developed by Dr. Jennifer DeEll that outlines the unique starch index values, firmness and internal ethylene concentrations at harvest for apples going into long-term storage.

Cultivar	Starch Index (1-8)*	Firmness (lb)	Internal Ethylene (ppm)
Ambrosia	2.5 – 4	> 17
Cortland	2.5 – 3.5	> 15	> 0.2 in
Crispin	3.5 – 4.5	> 17	> 0.2 in
Delicious (Red)	2.5 – 3.5	> 17	> 0.2 in
Empire	2.5 – 3.5	> 17	> 0.2 in
Gala	2.5 – 3	> 18
Golden Delicious	3 – 4	> 16	> 0.2 in
Honeycrisp	~ 5	> 15	Not useful
Idared	3 – 4	> 15	Not useful
McIntosh	2.5 – 3.5	> 15	> 0.2 in
Northern Spy	2.5 – 3.5	> 18	> 0.2 in

A Core-dinated Record

Be sure to keep track of the detail for future reference. Looking back to help determine the do’s and don’ts will pay off in the long-term. Remember to include:

• calendar date of harvest
• yield and other quality parameters (size, firmness, colour, weight)
• length of time stored/when apples were removed from storage (if you have access to this)
• pay out for crop
• it would be good to write down GDD and night-time temperatures for reference for the week(s) prior to harvest

Remember that these strategies should be used in collaboration with one another to give you a better idea of when to harvest.

For more information check out Dr. Jennifer DeEll’s articles on harvest maturity found below:

• ONcore Newsletter Vol.28 Summer 2024
• Orchard Network Newsletter Vol.26 August Issue 2022

A Rotten Situation

Harvest is the busiest time of the year, but the exact timing of when fruit comes off the tree has long-lasting impacts on both crop quality and orchard health. Picking too early or too late doesn’t just affect fresh quality – it can also set the stage for pest carryover, storage diseases, and physiological breakdown disorders.

Late-Hanging Fruit

From a pest management perspective, leaving apples on the tree past optimal maturity:

• Extends the window for insect pests like apple maggot, codling moth, and stink bug
• Increases overwintering survival and pressure for next season
• Leaves fruit more prone to sooty blotch, fly speck, black rot and bitter rot that can spread quickly preharvest, as well as during or after storage
• Encourages secondary colonizers (and major harvest nuisances) like yellow-jacket wasps to exploit overripe or damaged fruit

For more details on late season management and considerations for preharvest intervals, see the August 8th What the Crop?! Apple Update.

Any fruit that becomes overripe, cracked, or bruised is also more vulnerable to storage rots such as blue mold (Penicillum expansum) and gray mold (Botrytis cinerea). The risk is highest when fruit are harvested during wet weather, when spores are more easily spread. Overmature fruit with softer skin are also more susceptible.

Key harvest practices to reduce storage disease risk include:

• Harvest dry fruit whenever possible – avoid picking in the rain
• Cool fruit quickly – moving bins into cold storage right after picking reduces infection development
• Sanitize bins before use – to limit any pest carryover
• Handle fruit gently – to reduce bruising and micro-cracks that act as entry points for infection
• Harvest at the right maturity stage – not too ripe and not too immature

Having a Breakdown

Harvest timing also has a direct impact on postharvest disorders. If fruit are picked overmature – especially during warm fall weather – the risk of internal breakdown rises. This disorder shows up later in storage as browning and softening of the flesh from the core outward. Factors that increase risk include large fruit size, delayed harvest, and holding fruit too warm after picking

Lenticel breakdown is another issue that becomes more likely when harvest is delayed. This shows up as small, dark, sunken spots around the pores on the fruit skin. It is strongly influenced by cultivar (Honeycrisp and Ambrosia are quite prone), but risk also increases with fluctuating moisture before harvest, wet picking conditions, and overmaturity.

Both disorders are aggravated by rough handling, so gentle harvest and careful bin management are just as important as timing.