Answer: That sounds so frustrating! Based on your description, I am not certain what is happening to your petunias. Somtimes petunias are infested by budworms that are difficult to see. These are very small caterpillars that bore into the buds, and their excrement can seem like little black dots on the nearby foliage. However, it does wash or brush off. Petunias are sometimes affected by diseases that appear in mid summer, these can cause yellowing and die back as the main symptom. So I wonder if you might have a combination of problems. Since I am unable to identify the problem(s) with certainty, I would suggest you consult with your local Rutgers county extension. They should be able to diagnose the problem more specifically, and then based on knowing that, make recommendations on 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 maximum results. I'm sorry I can't be more definite for you.
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