Basil has become a favorite herb for growers and consumers alike. For growers, its short production schedule aligns nicely with many flowering bedding plants, making it an excellent addition to greenhouse product offerings.

What to watch for

A variety of diseases, such as Botrytis and leaf spots, can threaten successful basil production. However, the biggest threat to scout for is downy mildew. Basil downy mildew is caused by the oomycete pathogen Peronospora belbahrii and spread through contaminated seeds or wind-blown spores that can travel long distances. The pathogen establishes more readily in moderately warm temperatures and high relative humidity.

Plants infected with downy mildew will develop blotchy, yellow-to-reddish areas on the foliage between major veins, giving them a banded appearance. You may first spot symptoms in the lower foliage that gradually advance upward.

On the underside of the affected leaves, look for a fuzzy mat of spores corresponding to the blotchy areas. The sporulation color may vary from a brownish-gray to light purple, depending on the basil variety. The disease can spread rapidly through the crop if corrective actions are not taken.

Follow these cultural practices to reduce the risk of basil downy mildew:

• Provide adequate spacing to allow good air flow between the plants
• Irrigate early in the day to decrease relative humidity in the production area

Basil rotation program

Along with proper cultural practices, Syngenta has developed a preventive fungicide rotation to help ensure your success. This program features Subdue Maxx^®, Micora^®, Segovis^® and Heritage^® brand fungicides, which are registered to help protect basil plants grown for resale.

A well-structured program like this will provide guidance for leveraging strengths and modes of action of different products, to provide maximum benefit when needed most.

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© 2024 Syngenta. Important: Always read and follow label instructions. Some products may not be registered for sale or use in all states or counties and/or may have state-specific use requirements. Please check with your local extension service to ensure registration and proper use. GreenCast^®, Heritage^®, Micora^®, Segovis^®, Subdue Maxx^® and the Syngenta logo are trademarks of a Syngenta Group Company. All other trademarks are the property of their respective third-party owners.