Evaluation of fungicide programs for potato leaf brown spot and grey mold control, 2006

摘要

Potatoes (cut seed, treated with Maxim MZ 0.5D at 0.5 lb/cwt) were planted at the Michigan State University Muck Soils Experimental Station, Bath, MI on 25 May into two-row by 25-ft plots (34-in row spacing), separated by a five-footunplanted row and replicated four times in a randomized complete block design. Plots were irrigated as needed with sprinklers and were hilled immediately before the foliar fungicide sprays began. All fungicides in this trial were applied on a7-day interval from 28 Jun to 22 Aug (8 applications) with an ATV rear-mounted R&D spray boom calibrated to deliver 25 gal/A (80 p.s.i.) using three XR11003VS nozzles per row. Foliar late blight was prevented with foliar applications ofPrevicur Flex (1.2 pt/A) applied on a 7-day interval starting on 11 Jul. Weeds were controlled by hilling and with Dual 8E (2 pt/A on 25 May), Basagran (2 pt/A on 28 Jun and 11 Jul) and Poast (1.5 pt/A on 11 Jul). Insects were controlled withAdmire 2F (20 fl oz/A at planting and on 28 Jun), Sevin 80S (1.25 lb/A on 11 and 25 Jul), Thiodan 3EC (2.33 pt/A on 1 and 21 Aug) and Pounce 3.2EC (8 oz/A on 11 Jul). Plots were rated visually for percent of foliar area infected with brown leafspot on 24 and 30 Aug, and 11 and 18 Sep and Botrytis grey mold on 24 Jul, 17 Aug and 18 Sep. Vines were killed with Reglone 2EC (1 pt/A on 13 Sep). Plots (2 x 25-ft row) were harvested on 2 Oct and tubers were weighed and graded.Meteorological variables were measured with a Campbell weather station located at the farm, latitude 42.8269 and longitude -84.365deg. P-values (45oF base) were accumulated for each month from planting to desiccation; the total accumulated were187.4 from 25 to 31 May; 806.1 for Jun; 1642.3 for Jul; 2381.4 for Aug; and 2594.9 from 1 to 18 Sep (desiccation). Maximum and minimum soil moisture (% of field capacity) was 116.6 and 66.7 (Jul) and 119.1 and 80.4 (Aug) during which time severe flooding occurred. Precipitation was 2.93 in. (Jun), 6.77 in. (Jul), 3.47 in. (Aug) and 0.68 in. (Sep). Plots were irrigated to supplement precipitation to about 0.1 in./A/4 day period with overhead sprinkle irrigation.