Fungicide efficacy for management of Pythium root rot, 2012

摘要

An efficacy trial of several fungicides for control of root rot caused by Pythium ultimum on zonal geraniums was conducted in a greenhouse at the NWREC in Aurora, OR. The average minimum and maximum temperatures inside the greenhouse were approximately 48°F and 84°F, respectively. Day length decreased from 14hr 49min to 9hr 33min during the trial. Plants were started from seeds on 20 June. Six-week-old seedlings were transplanted to 4 in. pots with substrate composed of 45% mulch, 25% peat moss, 20% pumice, 5% vermiculite and 5% perlite and allowed to establish for two weeks. Initial treatment applications were applied as a drench on 7 Sept. Some fungicide treatments were reapplied 14 or 28 days after the first application (DAFA), as indicated inthe table. Plants were arranged in a complete randomized block design with 10 replications. Drip irrigation with Peter's Professional 20-20-20 fertilizer at 175 ppm and a 1:100 injection ratio began the day after transplanting on 2 Aug, for 3 minutes, twice daily. A known virulent strain of P. ultimum collected from nursery soils was used as inoculum. The inoculum was prepared by adding a 0.2 in. plug from a seven-day-old culture to 0.2 oz of sterilized millet seeds and incubating for 7 days. The plantswere inoculated 3 days after the first application of fungicide by mixing inoculated millet seeds and substrate used for potting in a 1:1 ratio. Each plant was inoculated with 0.7 oz of this mix by gently removing plants and adding the inoculum to the pot near the roots. To obtain root dry weight, the roots were then washed, placed in paper bags, and dried in an oven at 131°F for one week before weighing.