Evaluation of seed treatments and in-furrow treatments for dry rot and silver scurf control on potato, 2017

摘要

A field trial was conducted on Aroostook Research Farm, located in Presque Isle, ME in 2017 to evaluate seed treatment and in-furrow treatment effects on dry rot and silver scurf on potato. A randomized complete block design was used with four replications. Each plot consisted of three rows. Each was 25 ft long with three-foot row spacing and one ft plant spacing. Fertilizer (14:14:14) was applied at planting at the rate of 1,100 lb/A. Fusarium sp. inoculum was produced on autoclaved oat seed. The inoculum was placed by hand in the furrow, at the rate of 10g/ft, of the middle row at planting on 23 May. Potato (cv. 'Atlantic') hand-cut seed pieces were treated with chemical products on 23 May. Seed pieces treated with chemicals were planted and in-furrow treatments were applied by a handheld sprayer at planting on 24 May. Liquid seed treatments were applied in 6 fl oz water carrier per 100 lb seed, and sprayed on potato tubers within 5 hours of cutting. Powdered products were applied following liquid product and then mixed well with seed tubers. All plots were treated with Bravo WeatherStik (a.i. chlorothalonil) at 16 fl oz product/A to control late blight and Blackhawk (a.i. spinosad) at 3.6 oz/A to control Colorado potato beetle during the season. Emergence was evaluated on 19 June and 22 June. Emergence was assessed by counting the emerged plants per row of the 25 seed pieces planted and converting to percentage. Potato vines were killed with one application of Reglone (a.i. diquat) at 1.5 lb/Aon 25 August. Potato tubers in the middle row of each treatment were harvested on 13 September. The harvested tubers were washed, sized and weighed. The severity of tuber diseases was rated on 9 October. Tubers with diameters greater than 1 7/8 in. wereconsidered marketable yield. The rating scale for disease was based on the percentage of internal area of tuber tissue with dry rot or surface area affected by silver scurf: 0 (no symptom), 1 (1 - 5%), 2 (6 -20%), 3 (21- 50%), 4 (51 - 75%), and 5 (>75%). Disease index = 100 x Krt x n,-)/(Nx 5), where N = total number of plants evaluated, r is the level of severity from 0 to 5, and i = specific level of severity (from 0 to 5), and n = number of corresponding grade plants evaluated. All the data were analyzed using JMP (SAS Institute Inc., Cary, NC). For mean separation, Fisher's LSD was used on emergence and yield data, and Wilcoxon test was on disease measurement, both at significance level a = 0.05. Phytotoxicity was observed for this trial. No silver scurf was observed. Dry rot was present on tubers, but none of the treatments had a significant effect on tuber yield or disease index.