Apples Diseases Insects Pest Management Weeds

Apple Update: May 2, 2017

The OMAFRA Apple Team will be providing weekly crop updates reported from across the province, including growth stages, production, weather-related impacts, pest status and other issues affecting Ontario growers at the time. Continue following ONfruit for up-to-date crop information.

Crop Stages

  • In Essex County, apples are at pink to full bloom.
  • For the rest of Southwestern Ontario including Kent, Elgin, Middlesex and Norfolk, most varieties are at pink, with the exception of Idared at king bloom. Northern Spy are behind in bud development. There may be more king bloom inland.
  • In Niagara Region, apples are at tight cluster to pink.
  • In Grey County, apples are at tight cluster, Idared are at pink and Northern Spy are behind in development.
  • In Durham Region and Northumberland County, apples are at ½” green to tight cluster.
  • Further along the St. Lawrence and into the Ottawa Valley, apples
  • are at tight cluster.


On April 23rd, temperatures dropped below zero in many areas of the province. Localized areas within Kent, Norfolk and Niagara had frost with crop stages being at tight cluster to pink. Temperatures did not go below -2⁰C according to Vine and Tree Fruit Innovations, which is slightly above critical levels for 10% damage. In Durham Region, Northumberland County and Prince Edward County, temperatures dropped to -1.4⁰C to -3⁰C according to Environment Canada. Blossom stages in this area would have been green tip to ½” green, when critical temperatures for 10% damage are -7⁰C and -5⁰C, respectively. In Collingwood, Environment Canada recorded lows of -4⁰C but the apple blossoms were at ¼- ½” green in Grey County.

This past week there has been extensive rainfall, mostly occurring on April 30th and May 1st. Essex and Kent has received 15-40 mm, Norfolk has received 50mm, Niagara has received 30-90 mm and East of Toronto has received 65-80 mm. More rain is expected on Thursday and Friday and into the weekend. This doesn’t help with finishing pruning and getting started with tree planting.

There have been reports of weaker apple buds or light bud load. This could be due to last year having a good crop load after frost affecting the crop load in 2015. It could also be due to a very dry year last year with trees being weakened during bud initiation. After such a dry year, make sure to provide your orchard with the fertility it needs and start irrigating sooner into the season once the orchards have dried from all of these spring rains (especially with trickle irrigation).


Dormant copper has been applied in many orchards for fire blight to reduce overwintering bacteria that ooze out of cankers. Heavy rains occurring after application may have partially washed off the copper, reducing the effect of this treatment. Copper Spray or Copper 53 W should not be applied after ½” green as russetting may occur. Cueva is registered for season-long use and has a lower risk of phytotoxicity when used after a significant amount of green tissue is present.

Michael Celetti, OMAFRA’s horticulture pathologist has begun updating the regional fire blight prediction maps every Monday, Wednesday and Friday. Cooler weather from a cold front that passed through Ontario over the weekend has reduced the risk of fire blight infection in early regions with blossoms beginning to open. If fire blight was active in the orchard last year, the risk is remaining at caution, or where conditions will likely not lead to infection but could increase if weather becomes warmer.

During extended periods of caution in early bloom, biopesticides such as Blossom Protect, Double Nickel or Serenade OPTI could be used. This will help establish a baseline protection on open blossoms should conditions change quickly. These products form a protective layer on the blossom and prevent the fire blight bacteria from invading. In cooler temperatures, while infection may not be occurring, the fire blight bacteria can still multiply and remain on the blossom. If temperatures climb above 18⁰C, the bacterial population can then increase exponentially in a very short period of time. Consider biologicals as a safety net for situations like this. The product, Bloomtime is no longer distributed in Ontario.

Most regions have experienced at least 2 scab infections already, with earlier areas seeing their 5th to 6th potential infection this week. The rather wet spring we’ve been experiencing have many growers busy ensuring new growth is well covered. The heavy rainfall this week likely reduced the scab protection significantly. Even during ideal conditions (good coverage, full rates, dry weather), most protectant fungicides only offer 5 days of protection. During breaks in prolonged wetting events, many growers are opting to re-apply fungicides to replace residues washed off. For some, this is as often as possible to cover all blocks. Others are choosing to apply a product with good post-infection activity when conditions dry. Prebloom products like Scala, Luna Tranquility or Inspire Super provide good kickback activity particularly in cooler weather. Refer to Table 3-13. Characteristics of Apple Scab Fungicides in 2016-2017 Publication 360, Guide to Fruit Production for a list of other products with 48 hours post-infection activity.

High powdery mildew pressure last year followed by a mild winter has some growers concerned about management this season. A low rate (3-5 kg/ha) of sulfur can be incorporated into an early season protectant scab program in orchards with a history of powdery mildew until systemic fungicides with mildew activity are used. Some orchards with historically low powdery mildew pressure are using early season and summer oil sprays to help with suppression of this disease.

Growers that saw sudden apple decline last year in trees typically 3-8 years old are watching bud break closely. Movement at some of these orchards has been observed to be slightly slower in trees that were adjacent to those trees that collapsed and were removed last year. Contact Kristy Grigg-McGuffin (519-426-4322 or if you are seeing this issue.


European red mite activity has not yet begun though eggs can be easily found on fruit spurs in many orchards. Delayed-dormant oil has been applied in many regions and continues to be applied in the later areas for mite control. This can be applied up to tight cluster. Since oil works by suffocation, thorough coverage (>1,000 L water/ha) is important and is only effective on eggs. Monitor frequently to determine activity if oil has not been applied yet.

It was difficult for many growers to find an ideal window to apply dormant oil for scale due to the freezing night temperatures and/or windy conditions. Oil applications applied at this point may have some – though quite reduced – efficacy on scale. Overwintering scale began maturing before bud break and would now have a protective covering. Trials outside of Ontario have found varying levels of efficacy using insecticides registered for scale control such as Closer or Sivanto Prime at tight cluster to pink.

Traps for oriental fruit moth, apple leafcurling midge, San Jose scale and European apple sawfly are starting to go up. No biofixes have been set. Mating disruption for oriental fruit moth is also being applied in the earlier regions.

Growers that had issues with plant bug, leafcurling midge, European apple sawfly or spring feeding caterpillar in previous years are considering a prebloom insecticide. While pyrethroids do provide broad-spectrum management, this group of insecticides is harsh on natural enemies. Although beneficial populations may still be relatively low early season, there is the possibility of causing mite flare-ups by reducing the predatory mite complex.


Herbicides are being applied during the critical weed-free period, which is from bud break until 30 days after bloom Because we have had a mild winter and a long spring, winter annual weeds, such as purple dead nettle, common chickweed and dandelions are flourishing.


Refresh your knowledge of identification, biology and monitoring techniques for common insect and disease pests by attending the free Apple Scout Training workshop at the Simcoe OMAFRA Resource Centre on May 4 from 9:00 am to 3:00 pm. To register, please contact the Agricultural Information Contact Centre.

Save the date! Ontario Apple Growers Summer Tour will be held in the Niagara Region on July 5. More details to come.

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