Oozing thick amber sap on nectarine tree - Ask Extension
Our dwarf nectarine tree was afflicted with peach leaf curl last spring. We controlled it wi3copper fungicide. Late last summer it began oozing thic...
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Oozing thick amber sap on nectarine tree #892314
Asked February 05, 2025, 7:59 AM EST
Our dwarf nectarine tree was afflicted with peach leaf curl last spring. We controlled it wi3copper fungicide. Late last summer it began oozing thick amber sap in various places. Local nursery could not help with diagnoses or treatment. What do we do now?
Anne Arundel County Maryland
Expert Response
Oozing sap, also known as gummosis, can have several causes: a wood-boring insect, infection, physical damage, or tree stress due to environmental conditions. It can be difficult to tell what is responsible because the symptoms overlap greatly. Wood-boring insects and some pathogens are typically secondary problems, meaning that they take advantage of a weakened or injured tree but didn't cause the original injury or stress.
Neither borers nor infections in the trunk can be treated since, by the time symptoms are evident, some damage has already been done. However, sometimes the wounds are minor enough that the damage remains limited and the tree recovers on its own. All you can do is to make sure the trunk is protected from physical damage (mowers, string trimmers, deer antlers rubbing on the bark in autumn, etc.), monitor the tree for watering needs any time the weather is dry for long periods, and wait to see how it leafs-out in spring. Peachtree borer is the primary wood-boring pest of peach and related fruits (including nectarine), and it tends to target trees whose bark was cut by mowers or string trimmers or which are planted too deeply (where the root flare, the junction of roots and trunk base, sits below soil level instead of just at the surface).
Miri
Neither borers nor infections in the trunk can be treated since, by the time symptoms are evident, some damage has already been done. However, sometimes the wounds are minor enough that the damage remains limited and the tree recovers on its own. All you can do is to make sure the trunk is protected from physical damage (mowers, string trimmers, deer antlers rubbing on the bark in autumn, etc.), monitor the tree for watering needs any time the weather is dry for long periods, and wait to see how it leafs-out in spring. Peachtree borer is the primary wood-boring pest of peach and related fruits (including nectarine), and it tends to target trees whose bark was cut by mowers or string trimmers or which are planted too deeply (where the root flare, the junction of roots and trunk base, sits below soil level instead of just at the surface).
Miri
