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Ontario apple update: May 3

May 6, 2024  By ONfruit

Growth Stages

We are seeing mixed staging on the tree, meaning bloom hasn’t been uniform. This will make for a difficult thinning season, along with potential future challenges with late bloom.

Regionally, growth stages are fairly spread out depending on cultivar and proximity to water:

  • In Essex, Chatham-Kent, Lambton, Middlesex, Elgin, Norfolk, Brant and Niagara, most cultivars are at king bloom, or will be shortly. In early areas, more inland sites are full pink to full bloom.
  • In Grey, most cultivars are at early pink.
  • In Durham, Northumberland and Quinte, most cultivars are at tight cluster with some pink on early varieties.
  • Further along the St. Lawrence and into the Ottawa Valley, apples are at tight cluster, just starting to show pink.

Frost Update

Areas across the province have reported frost damage from last week’s low temperatures. Parts of the province reached as low as -6 °C, where most areas experienced between -1 and -3 °C. Damage has mostly been seen in the pistils, specifically in flowers at lower parts of the tree, affecting areas and varieties that were further advanced. We have a few more weeks until we are out of the frost-free days, but the forecast looks mild and hopefully it stays as such.


Disease Development


Most areas have experienced multiple apple scab infection events over the last couple of weeks. Earlier regions of the province are beyond 50% ascospore maturation, while later regions are at about 30-50% of ascospores matured. This means that for future rain events, expect large ascospore release and keep good fungicide coverage on those rapidly growing leaves. With temperatures above 15C, only 6 hours of leaf wetness are required for germination to occur.


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