Organic Materials Management

Compost Tea and Disease Suppression

In recent years, there have been a large number of grower testimonials suggesting that compost tea has improved their ability to manage plant diseases. Grower experiences have indicated that both compost extracts and teas can suppress the incidence and/or severity of foliar and root rot diseases.

Unfortunately, relatively few rigorous scientific studies have examined the use of compost tea for plant disease suppression. Of the scientific studies that have been done, some have indicated that both compost extracts and teas can suppress the incidence and/or severity of foliar and root rot diseases, while others have observed no significant effect.

However, the lack of consistency of disease suppression by compost tea may be caused by variability in raw materials, the production process, nutrients, and other materials tank mixed before application, application method and timing, pathogen pressure, and environmental conditions. To learn more about the views, concerns, and pro/con arguments on this issue, visit:

• Soil Foodweb, Inc.
• Compost Tea Task Force Report (Adobe PDF, 208 KB)
• National Organics Standards Board

Choosing the Right Tea

Scientists have tested various types of compost and compost tea for their effectiveness in controlling disease on different types of plants growing in different types of soils. While much of this work is preliminary, results suggest that matching the proper compost and compost tea recipe to the particular situation will give more benefit than using a "one-size fits all" approach.

For example, foliar diseases of vegetable row crops grown on clay or loam soils are best controlled with foliar applications of a bacterial compost-based tea, supplemented with molasses and kelp. However, when such vegetables are grown on sandy soils or in potting mix, a soil drench of compost tea based on compost made to produce a higher fungal content is more effective at controlling root diseases.

Compost Tea Homel

Last updated: April 23, 2008