First Report of Albugo lepidii Causing White Rust on Broadleaved Pepperweed ( Lepidium latifolium ) in Nevada and California

Summer outbreaks of white rust occur regularly on the leaves of the exotic invasive crucifer broadleaved pepperweed (Lepidium latifolium L.), which grows in riparian and poorly drained habitats of Nevada (NV) and California (CA). The white, spore-bearing pustules of the pathogen develop profusely on both the abaxial and adaxial leaf surfaces. This white rust was presumed to be the common crucifer disease Albugo candida (pers. ex J. F. Gmel) Kuntze, which was reported from L. latifolium in CA. Sporangia were observed from two isolates from NV (Reno and Elko) and two from CA, all sampled in July 2010. All were smaller in diameter (14.9 to 18.6 [mu]m) than reported for A. candida from CA. Total DNA was extracted from pustules scraped from L. latifolium leaves from the four sites. White rust pustules developed on 31% of L. latifolium plants with approximately 40 pustules per infested leaf. Preliminary host-range testing indicates that it warrants further investigation as a potential bioherbicide to control L. latifolium.