Evaluation of foliar fungicide treatments for control of soybean rust and downy mildew in Fairhope, AL, 2009

摘要

The trial was conducted to determine the ability of LEM17 EC and Picoxystrobin to control soybean rust (Phakopsora pachyrhizi) and downy mildew (Peronospora manshurica) in soybean. The field was subjected to four independent pre-plant applications: Roundup 1 qt/a to burn down winter weeds outside clover area (4 Mar); 190 lb/a 8-21-21 + 10 lb/a Sulfur + 0.5 lb/a B (15-40-40-10S,0.5B)(29 Apr); Prowl EC 2 pt/a, incorporated, and bedded (30 Apr); and Roundup 1 qt/a to stale beds (08 June). Plots were arranged in a randomized complete block design with seven treatments and seven repetitions. Asgrow 7330 soybeans were planted at a rate of 8-10 seeds/ft of row (12 June) in a Marlboro very fine sandy loam soil. Each plot consisted of 2 rows, 25-ft long, with 38-in spacing. Following planting, five sequential fungicide applications were made and one visual symptom rating was taken for both downy mildew (DM) and soybean rust (SBR). These applications follow according to DAP: Karate 2 oz/a + Tracer 2 oz/a, Reflex 1.5 pt/a + Poast 1 pt/a + Herbimax 1 qt/a- PDS (40 DAP); Karate 2 oz/a + Tracer 2 oz/a + Induce 1 pt/50 gal (59 DAP); first treatment sprays (60 DAP); second treatment sprays (80 DAP); and Steward 8 oz/a + Karate 2 oz/a + Induce 1 pt/50 gal (81 DAP). Plots were rated visually for DM at 91DAP using a 1-8 severity scale of symptomatic total canopy based on infected leaf area and SBR was rated at 119 DAP using the same scale. Plots were harvested mechanically on 16 Nov at 156 DAP. Data was then statistically analyzed by GLM and means and compared using Fisher’s protected least significant difference test.