Apples Diseases Insects Pest Management

Apple Update: June 8th, 2018

This post written by: Amanda Green, Tree Fruit Specialist, OMAFRA and Colleen Haskins, Acting Horticulture IPM Specialist, OMAFRA

The OMAFRA Apple Team will be providing 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.

In this update:

  • crop stages
  • thinning
  • diseases
  • pest activity

Crop Stages

Fruitlet stages range from 8 to 20 mm, with Georgian Bay area having smaller fruitlets and Niagara and Essex having larger fruitlets. Size also varies from variety to variety and proximity to a body of water.

Most areas are reporting a good fruit set, with some variability among the different cultivars.


Growers are in the midst of applying thinners or are applying their final sprays. Fortunately temperatures are getting warmer than what they have been, earlier in the week. With this recent cooler weather, you may have been waiting for warmer temperatures and are curious of how late is too late to thin.

  • With Sevin XLR, the label states that it is most effective when fruitlets are at 7-14 mm diameter and that you can apply up to 25 days after full bloom.
  • With Maxcel, the label states to apply between 5-15 mm and to apply a final application (if needed) before king fruitlets exceed 20 mm diameter
  • With NAA, the Fruitone L label states that it is most effective when fruitlets are 5- 10 mm diameter. Application when fruit is larger than 15 mm may result in misshapen or pygmy fruit in prone varieties.

If you get to the point of needing to apply a rescue spray, Michelle Cortens (née Arseneault), Perennia and Dr. John Cline, University of Guelph wrote an article on this subject in the April 2017 issue of the Orchard Network Newsletter.


Scab – some scab lesions have been found, but minimal at this time.  The degree day models suggest we have reached the end of ascospore maturity; however some areas have seen little rain over the past week and therefore remain protected until you are confident your orchard is free from primary scab.

Fire blight – some fire blight strikes have been noted in the Norfolk area, although overall across the province, reports of strikes are low.  Keep in mind that although most areas are well into fruit let development, any secondary or “rat-tail” bloom can lead to a fire blight infection, providing an excellent entry point for the bacterium to enter.  If you have cider varieties or young nursery stock, you may notice late blossoms and therefore protectant sprays for fire blight may still be required; otherwise, remove any unwanted lagging blossoms to prevent entry sites and risk of infection.

Powdery Mildew – very little reports of powdery mildew observed at this time.  One grower in the western region that had experienced high pressure in previous years, noted significant powdery mildew at the end of his rows where coverage is variable,  but elsewhere was clean.    It’s good to see protectant programs doing their job!

Pest Activity

Overall, Mullein bug and European Red Mite activity is being reported as low.

Codling Moth (CM):  Most areas set their biofix date last week as flight and trap catches increased rapidly with the hot weather, creating a range of 100-144 DDC.  Most areas noted they will be applying control products next week.

Oblique Banded Leafroller (OBLR): Traps have been placed in orchards across the province, with the first reported catch in Essex, but no catch in other areas.

Apple Leaf Curling Midge (ALCM): Larvae and eggs are being observed in curled terminal leaves, although pressure or infected terminals seems to be low at this time.

San Jose Scale (SJS):  We have been catching adults in traps over the past 1-2 weeks; however there is no evidence of crawlers at this time.  Crawler activity is expected over the next week.

Dogwood Borer (DWB):  Some flying adults have been caught in the London area this week.  Mating disruption for this pest has been reported as quite successful, and that after a 2-3 year period, activity from this pest is significantly reduced.


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