Sugarcane Fiji disease fijivirus
QA and TEM
Symptoms are described by Egan et al.(1989). The appearance of one or more galls on an otherwise healthy plant is the first sign of the disease. Galls occur on the veins, on the underside of the leaf base, on midribs, and on the outside of the leaf sheath, varying in length from less than 1 mm to 50 mm, 2-3 mm wide and 1-2 mm high. Galls may also occur in the vascular bundles of the stem. Infected plants have a grasslike appearance: leaves are dark green, very stiff and short. The leaves may have very irregular margins and the tops of the plant may be fan-like, as if chewed by animals ('bitten-off' effect) (Graham, 1971). The growing point may die and on some varieties axillary bud development gives a witches' broom effect. Plants do not recover from the disease: they become severely stunted and grass-like. On ratooning, they may eventually die.
Crop Losses/Economic importance:
Sugarcane Fiji disease (FDV) has been responsible for major losses of sugarcane in both Fiji and Australia.
In Fiji, the disease was first recorded in 1886, and by 1906 it was destroying thousands of acres of sugarcane (Daniels et al., 1971).
Further outbreaks occurred in the 1950's after the planting of susceptible varieties, and even by the early 1960's there were fields with 10 per cent infection (Egan et al., 1989).
Outbreaks still occur (Tamanikaiyaroi & Johnson, 1996). In Australia, the disease was noticed before 1890, but caused only occasional problems, and by the 1950's had been reduced to insignificance. However, after the planting of susceptible varieties major epidemics began in the mid-1960s and continued for a number of years, the peak being reached in 1979 when 70 million diseased plants were present in the Bundaburg district of south Queensland (Egan & Fraser, 1977). Overall losses were estimated at 5-7 per cent, with some farms and localities recording far higher figures (Egan & Ryan, 1986).
A method of assessing losses in cane yield due to FDV infection, involving random selection of stools and measurement of millable cane, has been described (Turner & Churchward, 1977).