Yellow leaves can follow drought or other water stress, oleander leaf scorch caused by a strain of Xylella fastidiosa, salt or boron injury, and sap-feeding pests such as oleander aphid or scale. Yellowing alone does not choose among them.
Oleander yellow leaves: possible causes
Read the pattern before changing care. Uniform yellowing or a central-vein pattern can follow drought stress. Scorch often starts at the tips or margins and spreads from one branch.
Plant coveredNerium oleanderOleander · outdoor garden
Check the leaves, stems and pot
Which leaves are yellow?
Yellowing can be uniform or follow the central vein under drought stress. Oleander leaf scorch instead often starts at the tips or margins, beginning on one branch and spreading.
Check whether yellowing affects all branches or one part of the canopy, whether leaves droop, and whether the pattern starts at the margins or tips. Inspect both leaf surfaces and new shoots for aphids, scale, caterpillars, honeydew or sooty mold.
Use the visible signs to choose the next check
Possible causes and next checks
Correct obvious water stress without keeping the root zone saturated and inspect leaf surfaces and new shoots for pests. If the branch pattern and progression fit suspected leaf scorch, use a qualified plant diagnostic service.
Watch for new damage or recovery
What to watch next
After a measured watering correction, observe whether uniformly yellow, drooping leaves recover. Continued branch-by-branch decline warrants diagnostic help. Recovery is not a stand-alone disease test.
Do not diagnose from one sign alone
What yellow leaves cannot tell you
Sources
- University of California Agriculture and Natural Resources Integrated Pest ManagementIdentification, lines 66-74; Management, lines 84-88.
- University of Florida IFAS ExtensionKey Plant and Recognition/Management sections for aphid, caterpillar, leaf scorch, and scale, lines 19-22, 34-37, 54-62, 83-119, and 126-134.
- University of California Agriculture and Natural Resources Integrated Pest ManagementPlant identification, optimum conditions, and pests/disorders index.