Evaluation of fungicides for control of hop downy mildew and powdery mildew, 2008.

摘要

Trials were conducted in a non-trellised research hop yard (cv. Galena) at the Washington State University, Irrigated Agriculture Research and Extension Center, Prosser, WA. Plots consisted of nine plants in a single row with 7 ftrow spacing and 3 ft plant spacing. Rows containing treated plots were separated by one row of non-treated hop plants. Treatments were arranged in a randomized complete block design with four replications. An overhead irrigation system wasutilized to create conditions conducive to disease development. Fungicide treatments directed to the 3 ft wide areas in which hop plants were growing were applied on approximately 2 week intervals beginning 1 May and ending 27 May with a Stihlbackpack mist blower (model no. SR420). Applications were directed sprays in 35 gal water/A. Aliette is currently registered on hop and was included as a “grower standard treatment” for comparison. Plots were inoculated on 2 May, 20 May, 24May, and 3 Jun as follows. Hop shoots systemically infected with downy mildew (spikes) were collected from a research hop yard at WSU-Prosser. To induce sporulation, spikes were misted with water and enclosed in a plastic bag overnight at roomtemperature (approximately 20deg C in the dark. Zoosporangia were harvested by shaking spikes in 0.5 gal water and straining through several layers of cheesecloth. Zoospores were allowed to germinate by maintaining this suspension at room temperature for1 hr prior to dilution to 4 gal water. This dilution was injected through the irrigation system and followed by irrigation of the hop yard for at least 5 hr. On 11 Jun plots were evaluated for downy mildew by counting the number of spikes per plant. Additionally, eight leaves per plant were arbitrarily selected and examined for the presence of powderymildew.