Dodder is a parasitic flowering plant. It is an extremely infectious pest that is hard to eradicate once it becomes established. It has a wide host range. Remove and destroy all infected plant material at the first sign of an infestation. Apply a properly labeled pre-emergent herbicide regularly to affected areas for the next three or four growing seasons to destroy the persistent dodder seeds as they germinate.
Most leaf spots start on lower leaves.
Many gradually increase in size to form large, dark brown to black areas. Others remain small and distinct but increase in numbers and begin to develop on younger leaves as the season progresses. Small, black, spore-forming pustules can often be seen in the spots when fungi are the cause. For more specific descriptions, see the various host plant sections that follow. Avoid overhead irrigation, especially late in the day.