Garden Mums: Upper leaf yellowing and necrosis
With the first operation, one cultivar had upper leaf necrosis and yellowing. These were grown outside, and the symptoms were advanced. Inspecting the lower foliage revealed they were still dark green, which helped discount the possibility that we were looking at a bacterial infection. The grower and I discussed other options, such as spray hytotoxicity and drought stress. Neither of these really seemed probable. Then the grower mentioned that the plants were grown without phosphorus.
Click here to read the complete e-Gro Alert report written by Brian E. Whipker at egro.org (PDF).