RESUMEN
Root rots in sugar beet storage can lead to multimillion dollar losses because of reduced sucrose recovery. Thus, studies were conducted to establish additional fungicide treatments for sugar beet storage and a greater understanding of the fungi involved in the sugar beet storage rot complex in Idaho. A water control treatment and three fungicides (Mertect [product at 0.065 ml/kg of roots; 42.3% thiabendazole {vol/vol}], Propulse [product at 0.049 ml/kg of roots; 17.4% fluopyram and 17.4% prothioconazole {vol/vol}], and Stadium [product at 0.13 ml/kg of roots; 12.51% azoxystrobin, 12.51% fludioxonil, and 9.76% difenoconozole {vol/vol}]) were investigated for the ability to control fungal rots of sugar beet roots held up to 148 days in storage during the 2012 and 2013 storage seasons. At the end of September into October, roots were harvested weekly for 5 weeks from each of two sugar beet fields in Idaho, treated with the appropriate fungicide, and placed on top of a commercial indoor sugar beet storage pile until early February. Differences (P < 0.0001 to 0.0150) among fungicide treatments were evident. Propulse- and Stadium-treated roots had 84 to 100% less fungal growth versus the control roots, whereas fungal growth on Mertect-treated roots was not different from the control roots in 7 of 12 comparisons for roots harvested each of the first 3 weeks in both years of this study. The Propulse- and Stadium-treated roots also reduced (P < 0.0001 to 0.0146; based on weeks 1, 3, and 4 in 2012 and weeks 1, 3, 4, and 5 in 2013) sucrose loss by 14 to 46% versus the control roots, whereas roots treated with Mertect did not change sucrose loss compared with the control roots in 7 of 10 evaluations. The predominant fungi isolated from symptomatic roots were an Athelia-like sp., Botrytis cinerea, Penicillium spp., and Phoma betae. If Propulse and Stadium are labeled for use on sugar beet in storage, these fungicides should be considered for root rot control in commercial sugar beet storage and on roots held for vernalization for seed production of this biennial plant species.
RESUMEN
To reduce storage losses and improve resistance to rhizomania caused by Beet necrotic yellow vein virus (BNYVV), studies were initiated to establish a storage cultivar selection program. In 2006 and 2007, 30 or more commercial sugar beet (Beta vulgaris) cultivars were grown in soil naturally infested with BNYVV. At harvest, two root samples from each plot were collected and used to establish percent sugar. Additional samples were placed on top of an indoor pile (set point 1.7°C) and inside an outdoor pile in a randomized complete block design with four replications. After 142 and 159 days in indoor storage, sucrose reduction ranged from 13 to 90% in 2007 and 57 to 100% in 2008. Outdoor storage sucrose reduction ranged from 13 to 32% in 2007 and 28 to 60% in 2008. An average of 31 and 45% of the root surface was covered with fungal growth in 2007 and 2008, respectively. Cultivars that retained the most sucrose had resistance to BNYVV and the least fungal growth and weight loss. Indoor storage with BNYVV-infested roots allowed for the most consistent cultivar separation and will potentially lead to selection of cultivars for improved storability and rhizomania resistance.
RESUMEN
Rhizomania caused by Beet necrotic yellow vein virus (BNYVV) and storage losses are serious sugar beet production problems. To investigate the influence of BNYVV on storability, six sugar beet cultivars varying for resistance to BNYVV were grown in 2005 and 2006 in southern Idaho fields with and without BNYVV-infested soil. At harvest, samples from each cultivar were placed in an outdoor ventilated pile in Twin Falls, ID and were removed at 40-day intervals starting at the end of October. After 144 and 142 days in storage, sugar reduction across cultivars averaged 20 and 13% without and 68 and 21% with BNYVV for the 2005 and 2006 roots, respectively. In the December samplings, frozen root area was 1 and 2% without and 25 and 41% with BNYVV for the 2005 and 2006 roots, respectively. Root rot was always worse with stored roots from BYNVV-infested soil in December, January, and February samplings. Root weight loss was variable in 2005; however, in 2006, an increase in weight reduction always was associated with BNYVV-infested roots. In order to prevent losses in rhizomania-infested areas, cultivars should be selected for storability as well as rhizomania resistance.