What is the defining moment that makes it too late to apply dormant oil spray to an apple tree? I live in East Vancouver.
Hi Alison: Sorry for the lateness of this response. For your area there may be spray restrictions that I do not know about that do not affect us as much here. To my knowledge the only real defining moment as to how late a dormant oil can be applied to most Fruit Trees is around 6-8 weeks before harvest. The main area of concern is not so much the dormant oil, it is what we mix in with the dormant oil which will then have some definite, defining relevance. As far as Apple trees, dormant oil can be used up to 6-8 weeks before harvest but honestly there is no real need to use a dormant oil late in the growing season unless we want to mix in an insecticide, perhaps a specific growth regulator and even that late in the season I will not use an insecticide at all on our Apples. In all of my years of growing Apples, I've never once used a growth regulator spray for the fruit. Sound cultural practices and dormant oil sprays after leaf fall (if needed) and one perhaps two applications prior to the popcorn stage of bloom are usually good enough (for us) unless we want to use the dormant oil as a mixing and better covering agent than water with another spray such as a fungicide or an insecticide. In our growing operation we never use a dormant oil by itself. We always mix in our Copper or Calcium based fungicides with the dormant oil. The primary purpose of a dormant oil used as a dormant season standalone spray would be to cover overwintering aphid and select mite eggs to prevent them from hatching, and to cover over any residual remnants of scale insects. Jim
