Knowledgebase
Fungus and cancers on fruit trees #757441
Asked June 21, 2021, 12:01 PM EDT
Larimer County Colorado
Expert Response
Hi Valerie,
Based on your description alone, my best guess is this is Cytospora, which is a type of fungus and very common on fruit trees. It tends to affect stressed trees (those that are suffering from drought, improper pruning, planting issues, etc.).
https://extension.colostate.edu/topic-areas/yard-garden/cytospora-canker-2-937/
Yes, you can remove the cankered limbs and throw them in the trash (do not compost). Between each cut, sanitize your pruning tools with 1:10 diluted bleach or Lysol. And the most important thing would be to improve the overall cultural health. Water appropriately; water in the fall and winter; mulch the base of the trees (keeping it away from the trunk); and make proper pruning cuts.
Hi Valerie,
The best way to reduce spread is to reduce overall tree stress--this means making proper pruning cuts, adding mulch, and watering properly. I wouldn't advise you scrape away any of the tissue because you can do more harm than good (and damage the cambium).
If the trees die, you can replace them in the same spot. This is not a soil-borne fungus. Again, if it is cytospora (which I cannot confirm because I haven't seen photos), this is a stress-related disease. So do your best to eliminate stress :)