On 2013 Oct 23, Andrew R Kniss commented:

This paper (on which I am a co-author) was an early report based solely on greenhouse and laboratory studies. Glyphosate applied to glyphosate-resistant sugarbeet increased disease under greenhouse conditions in this work. Our conclusions with respect to field management of the disease went beyond what the limited data could support. Subsequent research has shown over five field seasons, two growing regions, and 6 sugarbeet cultivars that the effect presented here is unlikely to occur in the field. Based on evidence presented in these subsequent works (outlined below), it appears that adoption of glyphosate-resistant sugarbeet is likely to have had no impact, or possibly even a positive impact, on Rhizoctonia root and crown rot management in sugarbeet in the US.

In an M.S. thesis by Youdon (http://search.proquest.com/docview/899255899), field studies using 2 sugarbeet cultivars over 3 field seasons failed to find any significant effect of glyphosate on Rhizoctonia root and crown rot in sugarbeet. Youdon's work further showed that the timing of glyphosate application in relation to disease infection had no impact on disease severity or incidence. Similar to the Larson et al. paper, glyphosate increased Rhizoctonia root and crown rot under greenhouse conditions. However, conventional sugarbeet herbicides caused greater disease than glyphosate. Therefore even if it is true that glyphosate can increase sugarbeet susceptibility to this disease, the conventional herbicides that glyphosate replaced would likely have even greater impact. A conventional herbicide control was not used in the Larson et al. paper, and therefore the conclusions were not relevant to real-world growing conditions.

In preliminary greenhouse studies similar to those conducted in the Larson paper, Barnett et al. (2012) http://www.bioone.org/doi/abs/10.1614/WS-D-11-00027.1 observed mixed results; glyphosate increased Rhizoctonia in one sugarbeet cultivar, decreased Rhizoctonia in a different cultivar, and had no effect on a third cultivar. A second set of greenhouse studies using 4 commercial sugarbeet cultivars showed no effect of glyphosate on Rhizoctonia severity. Glyphosate treatments also had no observable effect on Rhizoctonia root and crown rot in any of four sugarbeet cultivars conducted over two years in field studies.

On 2013 Oct 23, Andrew R Kniss commented:

This paper (on which I am a co-author) was an early report based solely on greenhouse and laboratory studies. Glyphosate applied to glyphosate-resistant sugarbeet increased disease under greenhouse conditions in this work. Our conclusions with respect to field management of the disease went beyond what the limited data could support. Subsequent research has shown over five field seasons, two growing regions, and 6 sugarbeet cultivars that the effect presented here is unlikely to occur in the field. Based on evidence presented in these subsequent works (outlined below), it appears that adoption of glyphosate-resistant sugarbeet is likely to have had no impact, or possibly even a positive impact, on Rhizoctonia root and crown rot management in sugarbeet in the US.

In an M.S. thesis by Youdon (http://search.proquest.com/docview/899255899), field studies using 2 sugarbeet cultivars over 3 field seasons failed to find any significant effect of glyphosate on Rhizoctonia root and crown rot in sugarbeet. Youdon's work further showed that the timing of glyphosate application in relation to disease infection had no impact on disease severity or incidence. Similar to the Larson et al. paper, glyphosate increased Rhizoctonia root and crown rot under greenhouse conditions. However, conventional sugarbeet herbicides caused greater disease than glyphosate. Therefore even if it is true that glyphosate can increase sugarbeet susceptibility to this disease, the conventional herbicides that glyphosate replaced would likely have even greater impact. A conventional herbicide control was not used in the Larson et al. paper, and therefore the conclusions were not relevant to real-world growing conditions.

In preliminary greenhouse studies similar to those conducted in the Larson paper, Barnett et al. (2012) http://www.bioone.org/doi/abs/10.1614/WS-D-11-00027.1 observed mixed results; glyphosate increased Rhizoctonia in one sugarbeet cultivar, decreased Rhizoctonia in a different cultivar, and had no effect on a third cultivar. A second set of greenhouse studies using 4 commercial sugarbeet cultivars showed no effect of glyphosate on Rhizoctonia severity. Glyphosate treatments also had no observable effect on Rhizoctonia root and crown rot in any of four sugarbeet cultivars conducted over two years in field studies.