Occurrence and severity of lucerne yellows disease in Australian lucerne seed crops

Production of lucerne seed is one of the most important seed industries in Australia. Anecdotal reports suggested that the disease lucerne yellows was having a marked impact on the industry, but no firm data existed on its occurrence and severity. An interview-based survey obtained detailed information from eight seedhouse offices and a telephone-based survey equivalent data from 62 individual growers. Only two of the 36 growers surveyed in New South Wales (NSW) and four of the 26 growers from South Australia (SA) had not observed the disease in their crops. In one instance the incidence of lucerne yellows was reported to be as high as 50-75 percent of plants but the majority of interviewees estimated the incidence to be less than five percent Responses from farmers in NSW did not indicate a significantly greater severity for the disease than was apparent in SA. The results from the seedhouses support those from individual growers in showing that lucerne yellows disease occurs widely in both States and that its severity is such that significant economic losses are likely.