Research Projects

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BBC Laboratories performed pathogen inhibition assays, testing the Xanthomonas pathogen against compost tea. These assays indicated strong inhibition.

The project was then taken to the field, where compost tea was applied at a 1:1 dilution using a drench nozzle. Treatments were applied twice at a six day interval to carrot seedlings with 6-10 true leaves in a random design within five, 300-foot rows. In all, there were ten 50-foot long treatment sections. The treatments were Control (water only), T1 (water + pathogen), and T2 (compost tea + pathogen).

Control plants (water only): tested negative for disease
T1 treatment (water + pathogen): tested positive for disease
T2 treatment (compost tea + pathogen): tested negative for disease

Although done on a relatively small scale and not rigorously replicated, we believe that these trials show that compost teas have an important role to play in the biological control of plant pathogens in organic and conventional growing conditions. It is our intent to explore this potential further during the next growing season.

Compost Tea Education and Research Foundation
Bejo Seeds, Inc.
Growing Solutions, Inc.
USDA-ARS Horticultural Crops Research Laboratory

Three 450-foot rows of carrots were seeded in August 2003. The experimental design is randomized complete block design with four blocks with all treatments replicated in each block. All treatments were applied to runoff using standard sprayers. All treatments were inoculated with the bacterial pathogen to ensure uniform disease pressure. Treatments are: 1—water control (plants treated with water), 2—spray adjuvants (ThermX70 and Nu Film 17), 3—compost tea, 4—compost tea + spray adjuvants. Compost tea was made in a GSI System25 using vermicompost and GSI Catalyst.

Year 1 objectives: 1) Determine the suitability of aerated compost tea for controlling bacterial blight of carrot caused by X. campestris pv. carotae on first year foliage; 2) Test spray adjuvants added to compost tea for enhanced control of bacterial blight on carrot foliage; 3) use epifluorescent microscopy and culturing techniques to quantify the abundance and distribution of phylloplane microorganisms on carrot foliage for each compost tea and control treatment; 4) Relate disease control to both the proportion of leaf area covered by compost tea microorganisms and the population of culturable microorganisms recovered from foliage.