Answer: This plant is generally pest and disease free, so there is no "usual suspect" to suggest. If the browning is along the margins or tips of the leaves then it is likely to be drought stress. It has been pretty dry this season and an occasional deep watering during drought could help. If there are distinct spots, then it might be a disease issue or feeding damage by an insect. I would suggest you consult with your local Rutgers county extension to get a more specific diagnosis. Based on knowing that, you can decide what to do. If a chemical control is needed, they will have the most up to date information on what to use and how/when to use it for best results.
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