Fruit Trees Infected - Ask Extension
My crab apple tree and my plum trees are secreting what looks like sap. My neighbor says the trees are infected with something and will die. Is there ...
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Fruit Trees Infected #927843
Asked April 08, 2026, 3:14 PM EDT
My crab apple tree and my plum trees are secreting what looks like sap. My neighbor says the trees are infected with something and will die. Is there anything I can do to stop this? I have uploaded a couple of photos from my crabapple tree.
Larimer County Colorado
Expert Response
Hi again,
The photos get a little too pixelated, but it looks like you have scale on the branches, which are hardened insects that feed on sap and can secrete honeydew (the clear ooze you're noticing).
I can't zoom in to determine what exact species it is, but most scale are treated in similar ways. The first would be to learn to live with it...many trees have scale and aren't affected by the insects. If you feel it's causing harm to the tree, then you can use a horticultural oil during the "crawler" stage - the young nymphs will hatch and be evident near the parent. The oils will smother the nymphs.
You can also use a systemic, such as the imidacloprid that you asked about in your previous question. HOWEVER, you must wait until the tree is done flowering, or you may harm bees and other beneficials. Read the label of the product.
I like this publication from the U of California because it's comprehensive: https://ipm.ucanr.edu/home-and-landscape/scales/#gsc.tab=0
The photos get a little too pixelated, but it looks like you have scale on the branches, which are hardened insects that feed on sap and can secrete honeydew (the clear ooze you're noticing).
I can't zoom in to determine what exact species it is, but most scale are treated in similar ways. The first would be to learn to live with it...many trees have scale and aren't affected by the insects. If you feel it's causing harm to the tree, then you can use a horticultural oil during the "crawler" stage - the young nymphs will hatch and be evident near the parent. The oils will smother the nymphs.
You can also use a systemic, such as the imidacloprid that you asked about in your previous question. HOWEVER, you must wait until the tree is done flowering, or you may harm bees and other beneficials. Read the label of the product.
I like this publication from the U of California because it's comprehensive: https://ipm.ucanr.edu/home-and-landscape/scales/#gsc.tab=0
