Submitted to: Phytopathology
Publication Type: Abstract Only
Publication Acceptance Date: July 28, 2005
Publication Date: August 5, 2005
Citation: Shishkoff, N. 2005. The effect of systemic fungicides on detection by culturing of Phytophthora ramorum [abstract]. Phytopathology. 95:S96. Technical Abstract: Rhododendrons with infections on expanding shoots caused by Phytophthora ramorum were sprayed with fosetyl-Al (3 g/L), mefonoxam (0.08-0.15 mL/L), propanocarb (1.5 mL/L) or water alone to determine if systemic fungicides can “mask” the presence of the pathogen. Immediately after spraying and weekly thereafter, leaf disks taken from the edges of lesions were plated on selective media. The organism could be recovered from control, fosetyl-Al and propanocarb-treated lesions at high frequencies (64-100 percent) immediately after treatment, and recovery of the pathogen declined thereafter. The pathogen could not be recovered from mefonoxam-treated lesions until 3-5 weeks after treatment, when low frequencies (3-13 percent) were found. In no case were symptoms suppressed; lesions were easily visible in all treatments. At the end of each experiment (3-8 weeks after spraying), remaining leaves on the plant, fallen leaves and samples of stem, bud, and root tissue were plated; the organism could sometimes be isolated from buds, fallen leaves and roots but the tissue with the highest recovery was stem tissue.