Occurrence and epidemiological aspects of potato silver scurf in California

Abstract

A new potato tuber disease has been observed in the Tulelake region, California, USA, since 1995, with tuber symptoms suggestive of silver scurf disease (Helminthosporium solani). In this work we isolated, identified and demonstrated the nature of the causal agent of this potato disease in California. In addition, the distribution of H. solani in potato fields and the inoculum potential at harvest time were investigated. Disease progress and H. solani spore populations were also characterised under commercial storage conditions. The main fungal genera associated with potato tubers in storage were Helminthosporium solani, Colletotrichum sp., Fusarium sp., and Rhizoctonia sp. The results of Koch's postulates indicated that H. solani is responsible for the outbreak of silver scurf in the Tulelake region. In a disease survey in three commercial potato fields naturally infested, H. solani infections occurred in all fields. However, the extension of the infections differed significantly between the fields. During potato storage, silver scurf usually increased over time. The percentage of the tuber surface covered by silver scurf varied from 3.5% up to 35.5% during the storage period. The number of H. solani lesions per tuber also progressively increased from 6% up to 35%, six months after storage. H. solani spore populations also increased over time in all studied potato stores; nevertheless, they followed no consistent pattern, exhibiting multiple and variable peaks of increase and reduction during the period of storage.

Potato soil-borne diseases. A review

“…are responsible for several superficial alterations called blemishes. Colonization by those pathogens is usually limited to superficial layers of tuber periderm (Harrison 1997;Stevenson et al 2001;Cunha and Rizzo 2004;Lehtonen et al 2008;Loria et al 2008) but they can colonize other parts of the plant until they reach vascular system. Streptomyces spp.…”

Parch srebrzysty (Helminthosporium solani) – objawy i zwalczanie

“…Tworzą się one na powierzchni chorych bulw przy wilgotności względnej powietrza powyżej 90% i temperaturach bulwy powyżej 3°C (Errampali i in. 2001, Cunha, Rizzo 2004, Johnson i in. 2014.…”