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Biofungicides for Tomatoes

Preventing tomato late blight

By: Sandy Feather ©2010
Penn State Extension

Q. I have been hearing about a new fungicide to control late blight on tomatoes called Serenade®. Can you tell me more about it?

A. Serenade® is a biological fungicide (biofungicide) that has a broad label to suppress and control many key diseases of fruits, vegetables and ornamental plants, including late blight on tomatoes. Biofungicides such as Serenade® are made from beneficial microorganisms such as bacteria and fungi. The active ingredient in Serenade® is the QST 713 Strain of Bacillus subtilis.


Serenade® has multiple modes of action to protect plants from pathogens. It inhibits pathogens from infecting leaves by preventing them from attaching to the leaf in the first place. If pathogens do manage to attach to a leaf, Serenade® outcompetes them for space on the leaf and inhibits their ability to absorb nutrients. It also destroys their ability to reproduce.

healthy tomatoes
Tomatoes at the market

Serenade® is approved for organic production by the Organic Materials Review Institute (OMRI). It can be used up to the day of harvest. Like most fungicides, Serenade® is most effective when used to prevent disease; it is not an effective “cure” once late blight gets started. The label recommends application every seven days, and it can be applied more frequently when disease pressure is high or when environmental conditions favor rapid disease development.


Late blight has been detected throughout western Pennsylvania again this year, including Allegheny County. Daytime temperatures between 70-80 degrees and nighttime temperatures between 50-60 degrees favor late blight, as does moisture on the foliage from rain, fog, dew or overhead watering.


If you are concerned about your tomato or potato crop, it is time to apply fungicides to protect them from late blight. In addition to Serenade®, copper-based fungicides are available for organic gardeners. Conventional gardeners can use fungicides that contain Daconil (chlorothalonil) to protect susceptible crops from late blight.


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