Effect of Amount and Time of Leaf Loss On Sugar Beet Yield and Quality.

North Dakota and Minnesota together produce about 57% of the United States sugar beet, (Beta vulgaris L.), crop.  Hailstorms that damage sugar beet leaves and sometimes kill plants are common during the growing season.  The objective of this research was to determine the effect of different amount of leaves lost in mid-July and mid-August on recoverable sucrose.  Research was conducted at Foxhome, Minnesota, and Prosper, North Dakota in 2010 and 2011.  The experimental design was a randomized complete block design with four replicates.  The treatments included manual removal of 0 (control), 4, 8 and 16 leaves per plant in mid-July or mid-August.  Individual plots comprised of two 9 m long rows spaced 0.6 m apart.  Fertilization was applied based on the requirement for sugar beet.  Weeds were controlled with multiple applications of glyphosate and Cercospora leaf spot was controlled with fungicide applications.  Roots were harvested and weighed in late September followed by quality analysis.  The tonnage and recoverable sucrose were different for the different sites.  However, across all sites and in both years, when compared to the control, recoverable sucrose loss consistently was significantly greater when 8 or 16 leaves were removed, and losses were higher when leaf removal was in mid-July compared to mid-August.  Recoverable sucrose losses when 4 leaves were removed were lower but not always statistically different from the control.  This research indicated that when sugar beet loses leaves, as during a hailstorm, plants may suffer reduction in recoverable sucrose and losses may be higher with more leaf damage and the earlier it occurs in the growing season.