I'm having a horrible time with powdery mildew on my verbena this year. It is all over my combo pots and straight verbena hanging baskets. I have sprayed with piperon and it didn't seem to be much help. I have downloaded your disease chart, but there are so many choices. What do you believe to be the best choice...I ususally use a ballfast fogger to spray so that might make a difference in what I choose.

Jennifer -

Chemical controls are obviously a necessity when powdery mildew gets out of hand but it is also important to remember that there are environmental factors contributing to the increased occurrence of the disease. Though different species will germinate at different relative humidity levels, in general high relativity is favored by the disease. When relative humidity is high plant leaves can remain wet for extended periods of time allowing spores to germinate. Cooler temperatures will also extend periods of leaf wetness. It is very important to first reduce relative humidity levels and minimize leaf wetness. Make sure that there is adequate spacing around each plant and provide horizontal airflow. You can also reduce relative humidity in the greenhouse by heating for brief periods allowing moisture on the leaves to evaporate into the air then venting the humid air out and allowing cooler, drier air in.

Even when you manage the environment the best you can, chemical controls are often times required. We have been successful at controlling the disease using products such as Cleary's 3336 or Fungo-Flo. Powdery Mildew can develop resistance so it is important to rotate chemical classes. We have also been successful with Zyban and Strike. Please consult individual labels for recommended methods of applications. You will get the best level of control by rotating these chemicals and making applications every 3-4 days until the disease pressure is significantly reduced. Then you can return to regular preventative treatments at 7-14 day intervals.

Jennifer, try strike at 4oz./100 with capsil.