I made the mistake of pruning one of my apple trees after the first frost as I'm leaving the country for 4 months. I now realize I should have waited until the first of March? If I have, what can I do to mitigate it?
Although the best time for pruning apple trees is early spring, it is not so critical error to prune those in the autumn. The reason, why it is not recommended to prune trees in the autumn, is that wounds do not heal so fast and risk of fungal infection somewhat is bigger then. If you see serious risk of infection, then you may cover those wounds with a special balsam, wax, wound dressing or simply oil paint. I personally prefer to leave tree wounds without any chemical treatment.
Where avoidance of spreading fungi during winter pruning is the goal this is accomplished by pruning shortly after midsummer. Trees aren't very quick about covering openings in the bark regardless of when these occur. Non-fungicidal treatments that form an airtight seal over the wound encourage fungal growth rather than suppress it.
How could pruning shortly after midsummer possibly avoid fungal infections of fresh tree wounds? If you live in certain climate, that has long dry period after midsummer, then maybe, but in temperate zone, especially its northern areas, this period is usually most potent for fungal infections, because of the warm and moist weather. Early spring is the best time for pruning, because first, it's still relatively cold then and this is not favourable for fungi. Second, spring is usually the driest season, and therefore open tree wounds would dry soon. And finally, spring is season of the most active growth of timber and bark, therefore wounds area would decrease most quickly that period. If to prune in the autumn, then weather turns colder again inhibiting fungal growth. Problem is, that after midsummers warm and moist period, there is usually lots of spores in the air, possibly highest concentration of the year, and spores can wait on the wound's surface until favourable temperature returns. Could you provide some links to researches, that confirm, that it is best to prune apple trees shortly after mid summer to avoid fungal diseases? Even oil paints have antiseptic properties.
If you live in certain climate You're - presumably - talking mostly about Estonian climate conditions while discussing a question posted by somebody who does in fact live in British Columbia.
I've been pruning all types of temperate fruit trees at any and every time of year for more than 40 years without noticing any signs of fungal infections or any other problems. However, I live in Burnaby, zone 8b; and the OP lives in Kaslo, zone 5b. Some apple varieties might suffer from winter kill in Kaslo; so, that might be a reason to avoid fall pruning there. Kaslo is significantly drier than Burnaby; I doubt that fungal infections will be a problem there.
No. I am talking about general conditions of Temperate Zone at BC-s lattitudes. Can you at least describe the mechanism behind your claim, that pruning apple trees shortly after midsummer avoids fungal infection risk, if links to some research results confirming the claim is too much to ask?
