Effect of silicon on the severity of brown rust of sugarcane in South Africa

Abstract

Silicon (Si) has been identified as a key element in the management of a wide range of pests and diseases in plants. This study focused on the effect of Si on the severity of brown rust of sugarcane caused by Puccinia melanocephala H & P. Sydow. The trial, repeated twice, consisted of eight treatments which included two different forms of Si and a control to which no Si was added. Plants were naturally infected by spores from brown rust-infected plants within a polytunnel. From three weeks after planting, plants were rated weekly for disease severity and these data were used to calculate an area under disease progress curve (AUDPC). All treatments ≥400 mg Si l−1 had a significantly lower final disease severity rating and AUDPC than the untreated control. No significant difference in disease severity was noted between the 1600 and 2000 mg Si l−1 treatments. A once off application of calcium silicate at a concentration of 1016 mg Si l−1, applied at planting provided the same reduction in disease severity as K2SiO3 applied weekly at a Si concentration of 1200 mg Si l−1. There was a significant negative relationship between the concentration of Si added and disease severity. A similar relationship was noted for the disease severity index and Si accumulation and deposition in the leaf. Results from this study showed a reduction in brown rust severity with an increase in Si content in the plant.