Gummy growths on cherry trees.

Question: Hello! Our community garden in Baltimore City has two 15+ year cherry trees. Recently, we have noticed these gummy protrusions on their trunks and large branches. Are they a disease that can be treated / means the trees need to be cut down? Thank you!

responder: Answered by the Home and Garden Information Center (HGIC), University of Maryland Extension. For timely gardening information and tips, subscribe to our Maryland Grows blog and quarterly newsletter. Follow us on Facebook, Instagram, and YouTube. Replied July 26, 2024, 2:39 PM EDT
response: Oozing sap is called gummosis, and it can have several causes ranging from wood-boring insects, bacterial or fungal infection, response to an injury, or simply stress from environmental conditions like high heat or winter injury, drought, or over-watering.  Cherry trees are unfortunately prone to gummosis and are also vulnerable to borers and infection, especially if they are first stressed or damaged by cuts to the bark. Are these fruiting cherries or flowering cherries? (Both can get much the same pest or disease issues and will be stressed by similar circumstances, but the prevention or management options may differ between plants producing fruit for consumption and ornamental trees that do not. The linked pages provide more information for each group.)  Unfortunately, if borers or infections are involved, there isn't much you can do except to minimize tree stress and see if they survive, since pesticides will not provide any benefit at that point. Methods to reduce stress include just making sure that they are monitored for watering needs during dry spells and our ongoing drought, and avoiding having mulch piled against the trunk and investigating if the tree is planted too deeply (if the root flare is not visible, for instance) so it doesn't develop problems like girdling roots.  If the canopy of each tree looks fairly normal and vigorous so far, then they might be okay, though sometimes canopy decline lags behind trunk symptoms of damage. If either tree does wind-up needing to be replaced, you can replant if you want new cherry trees, and early autumn is a great time to install trees if they are available. (Planting can occur in summer too, but watering needs will be greater, and nurseries tend to only refresh their flowering and fruit tree stock in spring and fall, so variety options may be few in summer.)  Miri

responder: The Question Asker Replied July 26, 2024, 6:05 PM EDT
response: Hello, thank you very much for your response!   These are two fruiting cherries, if that makes any difference in your recommendations for management/treatment.   Also, is there risk of the cause of the gummosis spreading? Near these cherry trees (both with the gummosis, although one worse than the other), we have blueberries and raspberries; then a little further away a rose bush, fig, and pawpaw; then much further away grapes and an apple tree.    On Fri, Jul 26, 2024 at 2:39 PM Ask Extension <<personal data hidden>> wrote:

responder: Answered by the Home and Garden Information Center (HGIC), University of Maryland Extension. For timely gardening information and tips, subscribe to our Maryland Grows blog and quarterly newsletter. Follow us on Facebook, Instagram, and YouTube. Replied July 26, 2024, 6:20 PM EDT
response: It could impact the suggested remedies, though management options are addressed on each of the cherry pages (flowering vs. fruiting) that we linked to. Gummosis can't spread itself, as it is the symptom of a problem, not the agent of damage itself (if there is a pest or disease involved). Borers usually target plants under stress, even if obvious symptoms of that stress are not yet manifesting. (Like drought...not all trees wilt readily even when drought stress has been going on for a few weeks. Different groups of borers can target over-watered plants, though that is not as likely in this case.) Canker infections can be more generalized in what they attack (the range of host plants can be large), but even then, it's usually weakened or injured plants that succumb to infection.  The other fruits you list are probably not at increased risk of this particular problem, but blueberries don't have great drought tolerance and should be monitored carefully for watering needs when rains are insufficient. Raspberries are about average in their drought tolerance, and would still do well to have stress minimized by being monitored periodically for watering needs. Fig has some innate drought tolerance, but as with many plants, too much stress from over- or under-watering could cause fruits to abort before they finish ripening. Roses will also rebloom at their best if they are watered when needed, though as with most things, try to water the soil in the root zone and minimize getting the leaves wet, as prolonged wetness on leaf surfaces can make them easier for spores to infect. (Different diseases from the cherry issue.) If this is unavoidable, water early enough in the day so that leaves can dry by nightfall. Pawpaw isn't too picky, but also might appreciate occasional watering if rains are inadequate, especially if you wanted fruits to reach their full potential for size and not drop early. Similar advice pertains to the grapes and apple about regular monitoring for watering needs...fruit of all types is mostly water and the ripening process uses lots of moisture, so irregularities in soil moisture availability can impact fruit quality, flavor, and size.  Miri