In spring 2026, I noticed that branches on my apple and pear trees turned black, and the bark swelled at the branch junctions. My neighbor says it's sunscald. How can I save the trees and prevent this next year?
When exactly in spring did you notice this - at the end of March or already in April when the thaws started?
Your neighbor is partly right, but it's not quite sunscald in the classic sense. Most likely it's temperature fluctuations: during the day when it thaws, the bark warms up and starts to "wake up," but at night the frost kills it. This hits hardest at branch forks, where the bark is thinner and less protected. The blackening is dead tissue, and the swelling shows that decomposition has already started under the bark.
As for saving them - damaged branches usually can't be saved. If the blackening is only on the bark, you can clean away the dead part in spring and disinfect the cut, but if the wood under the bark is black, the branch is already dead. Cut it off flush with the trunk so it doesn't get in the way. Going forward, the main thing is to prevent sharp temperature swings. Whitewashing the trunks and thick branches in fall before the first frosts helps: the paint reflects the sun and keeps the bark from warming up during the day. Wrapping young trees with non-woven fabric also makes sense. Also try to pick a planting spot so the trees don't stand in full sun on the western or southwestern side of the garden - that's where the temperature swings are strongest.
Bark swelling and blackening of branches in spring is usually a result of the wood and bark freezing at night and thawing during the day, with this cycle repeating many times in a row. The tissues can't handle this kind of stress, especially in branch forks where the bark is stretched tighter. If the bark has already swollen and darkened, it won't recover - you'll have to cut off the affected branches back to healthy wood.
For the future, the main thing is to protect the trunks and main branches by whitewashing them in fall (you can use special tree paint or even lime) and covering the lower part with burlap. The idea is to darken the bark so it heats up less from the sun in February-March and doesn't create that temperature difference. Also, don't prune branches in fall before the frosts - the wounds don't have time to seal and become vulnerable spots.
The main thing right now is to cut off the blackened branches down to live wood, otherwise the infection will spread further. Saw slightly above the healthy tissue, and treat the cuts with pruning sealant or oil-based paint.
For next season, whitewashing the trunks and scaffold branches in the fall will help - do it specifically before winter so the bark doesn't overheat on sunny days and doesn't freeze at night. The white layer reflects the sun, temperatures stay more stable, and those freeze-thaw cycles won't strip the bark off. Whitewash in October-November, and in spring after the snow melts, check if the whitewash has peeled off - if it has, do it again.
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