Rice false smut (Ustilaginoidea virens) in Egypt

Rice false smut (RFS) caused by Ustilaginoidea virens (Cke.) Tak. (Teleomorph: Claviceps oryzae sativae Hashioka) is a sporadic disease where rice (Oryza sativa L.) is Cultivated. RFS is a new disease in Egypt and appeared for the first time in the Nile Delta in 1997. This paper is the first record of RFS in Egypt. RFS was surveyed in most rice production areas of Egypt during two seasons. Disease incidence and number of spore balls (infected grains) were significantly higher in 2000 than in 2001. Disease usually affected a few grains (1-20) and might occupy any part of the panicle. The RFS fungus also attacks Echinochloa crus-galli, a common rice weed, as well as Imperata cylindrica, a common weed on irrigation canals in Egypt. The causal agent of RFS was isolated and identified on rice flour yeast extract dextrose agar (RYDA) and on PDA media. Yield losses caused by RFS ranged from 1.01 to 10.91%. Disease also reduced the chaff percentage and 1000-grain weight. Rice cv. 'Giza 171' was the most susceptible one, while cv. 'Sakha 102' was highly resistant. The amount of N fertilization was correlated with high disease. Early transplanting (at beginning Of June), cultivation in clay soil and spraying rice plants with Topsin-M or copper-oxychloride (each 2.5 g/l) at the beginning of booting stage significantly reduced the disease. Further studies are needed to investigate the viability of the fungal spores and sclerotia during winter, variation between fungal isolates, ability to produce mycotoxins and control of RFS disease using nonchemical methods.