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

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

Grower Grind

Fruitlets are hanging on in most regions where weather was great for chemical thinning application, but not great in terms of product efficacy. Challenging decisions regarding chemical thinning were made due to frost damage. Hand thinning is presumed to be relied on in many regions, where the cost of labour is top of mind, especially given that fruit simply isn’t dropping. Much of the province experienced some impressive rainfalls and winds over the last week (where many areas needed some rain, not the wind), but a break in the humidity has been welcome.

Growth Stages

Across the province Gala and Honeycrisp seem to have a decent crop, where Ambrosia is expected to have a little less. Fruitlets and terminals continue to grow at the Simcoe Research Station.

At the Simcoe Research Station, king fruitlets and terminals measuring the following:

	Honeycrisp	Ambrosia	Gala
Fruitlet Size	32.3mm	28.8mm	31.7mm
Terminal Growth	24.6cm	27.7cm	27.6cm

In contrast, 2025 showed the following sizes and terminal growth:

	Honeycrisp	Ambrosia	Gala
Fruitlet Size	34.8mm	28.6mm	29.7mm
Terminal Growth	15.7cm	15.8cm	18.1cm

Breezy Does It

Strong winds continue to persist over the growing season, which can cause damage of leaders, limbs, fruit drop, and even breakage of the graft union.

The best way to address wind issues is by understanding your landscape and how it can affect your orchard

Wind Mitigation

Hills, valleys, dense vegetation, and fencing all factor into wind patterns and aerodynamics. Be sure to consider these before planning or making changes to your orchard.

To mitigate wind issues consider the following:

• Windbreaks on windward side of orchard trees
• Orientation of rows, along the path of prevailing winds
• Support trees directly after planting
• Maximize strength of trellis systems and anchors
• Prune trees to fruit to hang away from limbs
• Prune limbs that may cause rubbing

For more information check out the following resources

• Weather Risks: strategies to Mitigate Wind Damage
• Designing and Caring For Windbreaks

Herbicide Drift?

Steps to follow when you suspect herbicide drift:

• 1. Diagnose the problem
• 2. Contact the appropriate people
• 3. Document all of the details

A more thorough review can be found here, including contact information for proper assessment:
You Suspect Herbicide Drift – Now What?

Fungus* Amoung Us (*And Bacteria)

Getting Twiggy With It

Several cases of Nectria twig blight have been reported in orchards across the province. This is a fairly common fungus to find in Ontario orchards, but is typically not a major pest of concern. In most cases, infections are scattered or confined to individual shoots. However, the disease can become more noticeable in blocks with significant dead wood, winter injury, fire blight cankers, or other sources that make ideal entry point for the pathogen.

One reason Nectria often attracts attention is that it can be mistaken for fire blight. Both diseases can cause shoot dieback and dead branches, but there are some key differences:

Feature	Fire blight	Nectria twig blight
Pathogen	Erwinia amylovora (bacteria)	Nectria cinnabarina (fungus)
Spread direction	Travels downward from tip/blossom	Travels upward from basal canker or node
Bacterial ooze	Often present (creamy or amber sticky liquid)	Absent
Spores/fruiting bodies	None, it’s a bacterial infection	Bright orange or pink fungal cushions (sporodochia) on dead wood
Severity	High – highly aggressive, can lead to tree death	Low – opportunistic, attacks stressed or wounded wood

During rainy periods, spores are released and spread by rain splash to fresh wounds and susceptible tissue. Incidence of Nectria twig blight can be more pronounced in years following a wet harvest and cold (injury inducing) winter.

Because the disease relies heavily on dead wood, sanitation remains the most effective management tool. Summer pruning is a good opportunity to remove infected branches (or trees if canker is on trunk) before additional spores are produced.

Feelin’ the Burn

With the winds out there, a quick reminder on managing trauma blight during times of unsettled weather. While temperatures have dropped back to relatively cool, limiting fire blight bacterial growth, physical damage from storms and gusty weather can create opportunities for infection.

If you are concerned or have active fire blight in the orchard, be sure to apply Streptomycin (PHI 50 days), 0.5-0.8% Cueva, or Oxidate as soon as possible after the trauma event (ideally 4-12 hours after). Anything applied later runs the risk that the bacteria will have already established and begun to grow, reducing the efficacy of the product.

Streptomycin will provide kickback activity for any infection already in the tree – to an extent, of course – whereas, Cueva and Oxidate are surface sterilants only (ie., will just kill the bacteria on the tissue surface before infection occurs).

Following a trauma event, continue with an immune boosting program, using products such as Regalia or Lifegard to help the tree better fight off infection. Other products such as Buran or Cyclone Plus can help as dessicants to slow the spread of shoot infection. Prohexadione-Ca (Apogee/Kudos) can also be continued to reduce vegetative growth.

For a full list of registered products, see Fire Blight on the Ontario Crop Protection Hub.

Bugs Behaving Badly

Ready to Roll

The biofix for the summer-generation obliquebanded leafroller (OBLR) has now been established in many regions with sustained adult trap catch. This kicks off the start of degree-day accumulation for egg hatch predictions.

What does this mean for management? Trap catch does not signal an immediate spray timing. Instead, it marks the starting point for tracking development and predicting when young larvae will begin hatching and feeding on foliage. The most effective control window targets newly hatched larvae before they become protected within leaf rolls or move to fruit clusters.

For more information on registered products, see Obliquebanded Leafroller on the Ontario Crop Protection Hub.

With fruit seeming to hold on in some regions this year, OBLR management will be all the more important. While OBLR larvae primarily feed on foliage, they often tie leaves or seek shelter in tight fruit clusters, particular where fruit hasn’t been thinned down to singles. As larvae move and feed within these sheltered areas, they can cause surface scarring where fruit are touching or where leaves are against.

Even relatively low OBLR populations can lead to noticeable damage when fruit clusters are crowded, making thorough thinning an important complement to management.

Jump Scare

Potato leafhopper are quite active though little hopper burn and leaf cupping have been reported. This damage is caused by a toxin in the leafhopper’s saliva that blocks vascular system flow, preventing normal movement of water and nutrients to the affected area.

In most high vigour blocks, leafhopper damage is manageable, particularly once terminals harden off. However, nursery trees and non-bearing blocks require control at first sign of injury since vigour and shoot growth can be significantly impacted. With the first cut of hay happening in many regions, there may be a flush of potato leafhopper moving into orchards in the coming weeks.

For more information on registered products, see Potato Leafhopper on the Ontario Crop Protection Hub.

Degree (Days) of Separation

Scale

Crawlers have been observed on monitoring tape in Norfolk County this week, which aligns with the forecasted emergence. At this point, all regions have reached the degree day timing for crawler activity (predicted emergence of 278 DDC).

For a full list of registered products, see San Jose Scale on the Ontario Crop Protection Hub.

Predicted emergence date of first generation San Jose scale, by region (biofix March 1st, base 10C)

Region	Current Degree Day Celsius (DDC)	Predicted Crawler Emergence (278 DDC)
Essex	442 DDC	Passed
Lambton, Middlesex, Elgin	324 DDC	Passed
Norfolk	348 DDC	Passed
Wellington	255 DDC	June 20
Niagara	338 DDC	Passed
Grey	280 DDC	June 16
Durham, Northumberland	259 DDC	June 19
Ottawa	282 DDC	June 16

Apple leafcurling midge

Apple leafcurling midge infested terminals have become more apparent in orchards this week. Most larva inside are orange, indicating later stages of development and are dropping to the soil to pupate.

Adult flight for the first generation has now come to an end for all areas. Early regions are entering into the second generation adult flight. Emergence predictions for the 2nd generation adults are summarized below. Emergence predictions for the 2nd generation are summarized below.

For a full list of registered products, see Leafcurling Midge on the Ontario Crop Protection Hub.

Predicted emergence date of first generation adult apple leafcurling midge, by region (biofix March 1st, base 9C)

Region	Current Degree Day (DDC)	5% Gen 2 (430 DDC)	50% Gen 2 (556 DDC)	95% Gen 2 (701 DDC)
Essex	512	Passed	June 21	>14 days
Lambton, Middlesex, Elgin	379	June 23	>14 days	>14 days
Norfolk	405	June 19	July 1	>14 days
Wellington	306	June 30	>14 days	>14 days
Niagara	396	June 20	July 2	>14 days
Grey	328	June 29	>14 days	>14 days
Durham, Northumberland	303	June 30	>14 days	>14 days
Ottawa	331	June 27	>14 days	>14 days

Want to Talk Heat?

Join us for another North American Orchard Meetup series to learn practical strategies and grower insights to tackle heat stress and maintain fruit quality – last webinar of the series on Thursday, June 25th!

For more information and to register, click on the post below:

Heat Is On: 2026 Virtual Orchard Meetup Series