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Plant Diseases/Gummosis (sap bleeding)

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Question
I have a young orchard in the rear of my property.  I planted the trees three autumns ago.  They were all very young and healthy when planted.  I have some experience with fruit trees; they are properly pruned and fertilized, as per schedule, as a result, they have tripled their size since they were first planted.  However, my red plum tree is causing me concern.  It is now about seven feet tall, and looks very healthy, except, it started oozing amber sap from its truck about two months ago.  The sap first appeared around a low branch that was pruned in the spring.  I didn't give it much thought, thinking it was just the result of the branch being pruned.  But now the whole truck, from about 6 inches to 18 inches off the ground, has started to ooze.  I have checked for borers and cankers, none of which seem apparent.  I do notice that the bark has cracked in places, which I attribute to the tree's rapid growth.  Could the oozing just be a result of this rapid growth? I live in the foothills above San Diego CA.  The moderate climate and the fertilizers have definitely contributed to the rapid growth of all the orchard trees.  I also have a peach and a nectarine, both of which exhibit no gummosis.  The oozing on the plum seems to have subsided.  I have fourteen trees, six of which, are citrus.  When I treated the citrus for citrus psyllid, I also treated the other trees in the orchard with the same liquid (systemic) insecticide, applied to the soil at the drip line.  The label stated that the product could be used on other fruit trees also.  Any thoughts?

Answer
Dear Kirk, First, I would like to caution you about the use of systemic insecticides for fruit trees.  It it true that they can be used for citrus and other fruit, however, bear in mind that any systemics will effectively poison the entire tree - including the fruit.  Generally, you have to make sure that you apply it after blooming season (since it can also poison the bees that pollinate the tree) and you have to discontinue the use long before the fruit is ripe.  I would suggest that to control the citrus psyllid and other such pests you could use a Neem spray which will not affect beneficials and doesn't leave a residue in the fruit.  You may have to watch your trees more closely, but I think the added benefit of growing more organic fruit may well be worth it.  As far as the plum tree is concerned, it sounds like your tree has such serious problems, that it might be worthwhile to simply remove it for the overall health of your orchard.  If the trunk is split all the way around, the tree will eventually die from these splits.  Often they are caused simply by the growth of the tree, so that as a tree grows, it will sometimes cause the thin bark to split.  This is often noticed in late spring after the winter months.  Avoid fertilizing fruit trees in the fall, as this causes more growth in the winter which may cause them to split more often.  Unfortunately, many 'experts' will still recommend fertilizing in the late fall, but this is a bad idea, especially if you already have splitting.  As you have noticed yourself, the fertilizers and moderate climate will make the tree grow more quickly, causing more opportunities for this problem.  So, if your tree is split all the way around the trunk, you might opt to remove it, since it will likely die within a year or so.  If it isn't that badly split, prune off bad areas, and avoid fertilizing until the normal spraying/fertilizing schedule instructs you to do so in the late winter.  The incidence of splitting should start to decrease when the fertilizer use is lessened.  I hope this information helps you, but write back if you have further questions.  Good luck, Melissa

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Melissa Johnston

Expertise

Plant diseases, landscaping, tropical plants, roses, herbs, plant care, grafting, horticulture, plant identification, anything about plants I can likely answer.

Experience

35 years experience in various plant businesses, 1984 Certified Texas Master Gardener.

Organizations
Master Gardener Association of Texas charter member

Publications
none as of yet, but I have a plant q&a book I am in process of submitting.

Education/Credentials
Magna cum laude graduate of Texas A&M, 1978

Awards and Honors
Plant growing awards, highest grade for Texas Master Gardener graduates.

Past/Present Clients
Past member of Allexperts.com and was very highly rated. Owned landscape company in the past, Almost Paradise, and was very successful despite little equipment, no help, and no advertising. Lived well for two years until 9/11.

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