Damping Off Disease an Organic Issue

BOZEMAN - Jun 5/08 - SNS -- Damping off disease in chickpea seed and seedlings is a problem in cool, wet springs, especially for growers trying to control the disease using only organic methods, say Montana State University master's degree candidate Rachel Leisso of Wisconsin and MSU Extension Plant Pathologist Mary Burrows.

The pair tested several biological control agents under Montana conditions. Chickpeas, also known as garbanzo beans, are a minor crop in Montana. However, Montana growers have been interested in organic strategies to control diseases, because organic chickpeas can command a higher market price.

Biological control seed treatments contain beneficial microorganisms that defend plants against pathogenic microorganisms, said Leisso. They have been successful controlling seedling diseases in other legume crops, but when Leisso began her master's work, little was known about their ability to protect chickpeas from damping off disease.

Leisso's task was to test the ability of commercially available biological control seed treatments to manage chickpea damping off disease both in greenhouse trials and at three Montana field locations in 2007.

Leisso tested six biological control treatments in greenhouse trials, and took three of those to tests in fields near Bozeman, Huntley, and Sidney.

The treatments tested in field trials included two bacteria-based biological control treatments, Kodiak which contains Bacillus subtilis and Yield Shield, which uses Bacillus pumilus, and one fungus-based biological control, T-22 Planter Box, which contains a strain of Trichderma harzanium. These were compared to standard chemical seed treatment with Apron XL LS, containing mefenoxam, and Maxim, containing fluidoxonil. The chemical treatments were tested both as separate treatments and in combination with biological control seed treatments.

"At all three locations, biological control seed treatments were not effective in managing damping off" Leisso said.

The mefenoxam (Apron) treatment was the most effective at all sites for control of disease. Results for Kodiak were promising at some sites, but were inconsistent between greenhouse and field trials, and from site to site within the field trials.

Burrows said that based on the tests so far, organic growers trying to manage chickpea damping off disease should plant later in spring to avoid cool and wet soil conditions and plant high quality seeds with optimal potential for growth.