Twig and leaf die-back on Zelkova Serrata - Ask Extension
Please see the attached photo of what looks like some form of rust or scale on my eight year old zelkova serrata that appears to be the likely cause o...
Knowledgebase
Twig and leaf die-back on Zelkova Serrata #462117
Asked June 13, 2018, 5:04 PM EDT
Please see the attached photo of what looks like some form of rust or scale on my eight year old zelkova serrata that appears to be the likely cause of some leaf and twig die back on the lower story of the tree.
Need to know what I can do to prevent loss of the tree.
Jackson County Oregon
Expert Response
There are two likely culprits that could be affecting your zelkova tree: a phytophera disease organism or a wooly elm aphid. It is very difficult from your one small photo to see the actual twig damage that is occurring.The phytophera stem-rot usually forms cankers on the twigs or branches and actually kills a section of the branch or twig tissue, which then causes the rest of the twig to die.It usually does not affect the leaves, however. A more likely suspect is the wooly elm aphid or the green peach aphid. Either of these pests flies in spring or overwinters on the tree and hatches out in spring. Either can cause twig die-back and ultimately leaf death.
Please take a sample of what appear to be insects on the twig, along with some dead twigs and leaves to the plant clinic at the OSU Extension office at 569 Hanley Road (Rte 238), Central Point.They can examine the twig and leaves and insects under a microscope for a definite identification. The clinic is open Monday through Friday, 10 to 2. The phone is<personal data hidden> for further information on how to get a sample to the clinic if you cannot go in person. You can also consult the Pacific Northwest Handbook on Insects and the one on Disease. Search on zelkova disease, wooly elm aphid, common nursery pests, and phytophera sem-rot to access materials that may be helpful in identifying your problem as well as treatments you can use to rid the tree of the problem.Access these materials at pnwhandbooks.org. Best wishes for rooting out the culprits!
Please take a sample of what appear to be insects on the twig, along with some dead twigs and leaves to the plant clinic at the OSU Extension office at 569 Hanley Road (Rte 238), Central Point.They can examine the twig and leaves and insects under a microscope for a definite identification. The clinic is open Monday through Friday, 10 to 2. The phone is<personal data hidden> for further information on how to get a sample to the clinic if you cannot go in person. You can also consult the Pacific Northwest Handbook on Insects and the one on Disease. Search on zelkova disease, wooly elm aphid, common nursery pests, and phytophera sem-rot to access materials that may be helpful in identifying your problem as well as treatments you can use to rid the tree of the problem.Access these materials at pnwhandbooks.org. Best wishes for rooting out the culprits!
Hope you are still tuned in. A very knowledgable other expert, Jean Natter, has suggested another culprit in the case of the damaged zelkova twigs and leaves. Indeed, the insects on the twig appear to be soft scale insects. Such insects suck juices from the twigs and deposit "honeydew", essentially bug poop, on the leaves. Jean suggests you view the following website about "Calico scale" to compare both photos and description of the insects on your tree. The website, from Ohio state University, also mentions possible treatments to rid the tree of the problem. Website address: //bygl.osu.edu/index.php/node/1022 Thanks go to Jean for setting the record straight!
