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

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

Production

Fruit continues to size and develop colour with early varieties being harvested in the southwest region roughly 14 days ahead of normal. In other areas, we anticipate between 7 to 10 days ahead of normal.

Harvest Maturity Predictions

Areas across the United States are seeing early harvest as well, where Michigan has been predicting since early July that apples would be harvested early in various regions. Highlighting a few varieties from the links provided, Table 1 compares predicted harvest dates and normal harvest dates in Grand Rapids.

Table 1. Normal* and predicted 2024 peak harvest dates for varieties for the Ridge area of Grand Rapids

Variety	Normal*	Predicted
Empire	September 24	September 14
Fuji	September 29	September 19
Gala	September 10	August 26
Honeycrisp	September 18	September 3
Idared	October 10	September 26
McIntosh	September 15	September 1
Red Delicious	October 5	September 23

For more information, see:

• Grand Rapids Michigan Harvest Maturity Predictions
• West Central Michigan Harvest Maturity Predictions

Apple Maturity Model

Michigan State University has developed an Apple Maturity Model based on bloom time throughout the state. Although this is something that has been released, it is still being developed and should only be utilized as an indicator for potential harvest dates. Other methodologies that aid in predicting apple maturity are covered in the article titled “Field Tools to Determine Apple Maturity” found in the August 2022 ONcore Newsletter.

Ambrosia Colour Chart

Ambrosia is an important cultivar where storage is important for the longevity of the variety. Dr. Jennifer DeEll has written an article (“Ambrosia Harvest Maturity for Storage” in the August 2022 ONcore Newsletter) specifically addressing challenges and mitigatory measures related to harvest indicators for Ambrosia.

If you are an Ontario apple grower, please reach out to Kelly Ciceran to get your hands on an Ambrosia Colour Chart to aid in your harvest timing decisions.

Delaying Apple Harvest

If growers are looking for additional information on how utilize chemical tools to stagger and schedule their harvest, ReTain and Harvista information can be found at the links below:

Pest Activity

With the heat and frequent rains, lush growth continues in many blocks, especially young plantings. In some cases, terminal bud set has reverted with new leaves expanding. Actively growing terminals remain susceptible to pests such as powdery mildew, fire blight, leafcurling midge, aphids and potato leafhopper.

This season has certainly been one for favourable conditions for disease development and many blocks are feeling the burn. Scab, powdery mildew and now the start of various summer diseases such as bitter rot can be found in most regions. Maintaining a regular protectant program will be needed until harvest if any of these diseases are present in the orchard, especially during wet and/or humid weather.

In general, conditions have also pushed insect emergence and development ahead of ‘normal’ for pests such as plum curculio, apple maggot, Japanese beetle and leafhopper. However, there have also been some pests such as codling moth and scale where activity within a generation has seemed to drag on. For scale, there may be some overlap in crawler activity of the first generation, which began emergence in mid-June and the second generation, which has just begun in most regions.

While the likely early harvest will undoubtedly take most attention, keep monitoring regularly. Activity for some such as apple maggot, codling moth, oriental fruit moth, scale, scab, fruit rot and fly speck/sooty blotch will continue until harvest. Control may be warranted if pest activity is high, impeding growth/photosynthesis, reducing fruit quality or lowering winter hardiness of limbs.

For more information on control strategies for some of these pests, refer to previous ‘What the Crop’ updates such as July 5th and June 21st.