Management of Rhizoctonia root and crown rot of sugar beet with banded applications of Proline, 2008

摘要

Research plots were located at the University of Wyoming Sustainable Agriculture Research and Extension Center in Lingle, WY. The soil was a clay loam and the field plot received overhead irrigation as needed. Four foliar banded fungicide treatments were evaluated for Rhizoctonia root and crown rot (RRCR) management in sugar beet. The field plot was planted on 14 May (replant) and a randomized complete block design with four replicates was established. Each treatment plot was 20-ft long and four rowswide (30-in. row centers) with a 5-ft nontreated in-row buffer. Plots were handweededas necessary. The inoculations, treatments and data collection involved the center two rows. Baseline sugar beet stand counts were determined on 24 Jun. All applications were made in a foliar band (7-in. width) to the plant crowns on 25 Jun (8-10 leaf stage immediately prior to inoculation). Treatments were applied with a portable (CO2) sprayer in a total volume of 1.06 gal/1000 ft at 45 psi boom pressure. The boom was equipped with a single-nozzle (8002 flat fan tip). Immediatelyfollowing the 25 Jun treatment applications, Rhizoctonia solani (AG2-2) inoculum produced on dried grain was applied to the crown of each plant (0.02 oz per crown). Immediately following inoculation, plots were cultivated to introduce field soil intothe crown and plots were watered the following week with 1.0 in. of water to favor infection. Crown rot incidence was rated on 11, 28 Jul, and 12 Aug and was reported as a percentage of the 24 Jun stand. Infected beets were those that had rapidlywilting leaves, darkened petioles and/or decayed crowns with necrotic leaves. An area under the disease-progress curve (AUDPC) was calculated for disease incidence data from 25 Jun (time zero) through 12 Aug. Additionally, plots werevisually rated for the percentage of total canopy necrosis present on 11, 28 Jul and 12 Aug and an area under the necrosisprogresscurve (AUNPC) also was calculated for this data collection period. On 8 Oct, one of the two treated rows (20 ft) were mechanically harvested and root yields were determined. All data were analyzed using ANOVA. A portion of the data are summarized below.