Utilizing boron to improve sugarbeet yield, quality, and resistance to Cercospora beticola.

Abstract

Cercospora beticola, the causal pathogen of Cercospora leaf spot (CLS), is one of the more severe foliar pathogens capable of causing damage to sugarbeet. When not managed appropriately, CLS can reduce sugarbeet yield 40%. Although plant defoliation caused by the disease directly impacts root size and sugar quality, other factors including leaf regrowth and impurities within the root affect plant health and crop quality. Management strategies including boron-containing compounds have shown to have fungistatic properties with potential to reduce disease severity in the field. Field studies were established to investigate the effects of foliar applied boron (B) on sugarbeet plant health and CLS disease severity. Treatments included a standard fungicide program, three foliar boron treatments (0.11, 0.28, or 0.56 kg sodium tetraborate ha^-1) applied at 10-14 day intervals without a standard fungicide program, three foliar boron treatments (0.11, 0.28, or 0.56 kg sodium tetraborate ha^-1) applied at 10-14 day intervals in conjunction with a standard fungicide program, and a nontreated check for a total of eight treatments. Application of foliar B did not reduce CLS in field environments across site years. In vitro analysis of C. beticola response to B demonstrated lower EC₅₀ values with sodium tetraborate than boric acid. Reduced control options, increased CLS resistance, lack of response to previous B applications, and varietal improvements may enhance the need for further evaluation of alternative controls. In-field evaluation of various B timing, increased B concentration, and addition of B-containing compounds may contribute to future CLS control.