First report of rust caused by Puccinia arachidis on peanut in South Carolina.
In September 2016, several groundnut plants exhibiting numerous rust-coloured pustules characteristic to peanut rust on abaxial leaf sides were observed in 2 plots at approximately 5% incidence of total leaflets (∼3% severity) in a localized area of approximately 2 × 2 m in a groundnut field in Blackville, South Carolina, USA (Barnwell County), on the commercial cultivar Georgia 12Y. Also in September, identical symptoms were observed in a localized area of approximately 3 × 3 m (80% leaflet incidence and 40% severity) in a commercial field (∼40 ha) of Georgia 06G (industry-standard runner cultivar) in Orangeburg County, South Carolina. The causal pathogen was isolated and identified as Puccinia arachidis based on morphological, molecular and pathogenicity analyses. This is thought to be the first report of rust caused by P. arachidis on groundnut in South Carolina, USA.