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United States Department of Agriculture

Agricultural Research Service

Title: Suppression of Phytophthora Infestans by Essential Oils and Natural Products in Lab Assays and Growth Chamber Studies


Submitted to: Northeast Potato Technology Forum Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: March 2, 2004
Publication Date: March 9, 2004
Citation: Olanya, O.M., Larkin, R.P. 2004. Suppression of phytophthora infestans by essential oils and natural products in lab assays and growth chamber studies. Northeast Potato Technology Forum Abstracts. pg 29

Technical Abstract: Control of late blight using alternative products is important in order to reduce fungicide inputs and costs for potato production. The objective of this study was to evaluate the effectiveness of essential oils and natural products for control of Phytophthora infestans in lab and growth chamber assays. Rye B media amended with essential oils (Lavender, Thyme, Thyme Borneal, Oregano), Ridomil Gold, and Serenade (bio-pesticide ' Bacillus subtilis strain QST 713) were evaluated for potential inhibition of growth and sporangial productions of P. infestans isolates relative to a non-amended control. In-vitro growth of P. infestans was significantly inhibited on media amended with Serenade and Oregano (P<0.01). Mean colony diameter (mm) of fungal growth was 6 and 6.5 mm on media amended with Serenade and Oregano, respectively compared to 44.7 mm for control after 21 days of incubation at 18 C. No sporangia production was detected on media amended with Serenade at 100 or 1000 ppm. In growth chamber experiments, bio-pesticides (effective microorganisms [EM], serenade, compost tea), oregano or Bravo were evaluated for late blight control subsequent to products application and inoculation of plants with P. infestans. Effective control and partial suppression of late blight development was observed on potted plants treated with Bravo and Serenade respectively. Lower suppression of disease was observed relative to the untreated plants when oregano or EM was applied. These results indicate that natural products may be partially effective for late blight control.

Last Modified: 4/22/2015
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