Has anyone thought to do tests for plant virus on plants that have this problem?
Not that I recall, it doesn't really fit the pattern for a virus. The leaf streak fungus, Aureobasidium microstictum, has been isolated from several samples of spring sickness, and has reproduced something like it when injected into the plants. But the question then is how does it get into the plants naturally, which is why we think there is likely a pest involved.
Greg, what systemic did you use? Have you tried treating half the garden and not the other half and then counting affected fans in both?
