In the production of grass seed, loss from blind seed disease occurs through a reduction in germinable seed since infected seeds are ungerminable. In addition, seed lots with germination below certification limits, or below seed contract standards, are of less value and in some countries are unmarketable. Presence of G. temulenta in import seed shipments may result in rejection of the seed by some countries (Halfon-Meiri 1978).
Australia. Blind seed was reported to cause few crop failures, although in 1969, 2,400 out of 9,000 acres could not be certified because of blind seed disease (McGee 1971a).
Denmark. A low level of blind seed was found in 6 percent of ryegrass samples exported from Denmark to Ireland (Lafferty 1948). A low level of blind seed was also found in 1957 (Kristensen and Jørgensen 1960).
England. In 1938 and 1939, germination as low as 50 percent was common in ryegrass (Noble and Gray 1945). In 1940, an average of 26 percent of ryegrass seed from south England was infected (Gemmell 1940).
The Netherlands. In 1965, the level of infection with the blind seed fungus ranged from 0 to 94 percent, with an average infection rate of 19.2 percent (de Tempe 1966).
New Zealand. Between 1931 and 1934, cost of seed lost to blind seed was estimated at £1,975-4,382 (Gorman 1939). In 1938, average germination of ryegrass was 67-76 percent in Christchurch, Canterbury, and South Canterbury (Hyde 1938b). Greenall (1943) reported germination of ryegrass as low as 1 percent. Greenall also noted that the severity of blind seed disease depended on environmental conditions, and he expected that in South Otago one year in every two or three would be accompanied by poor germination. During 1944-1946, 45-84 percent of samples from the South Island had more than 20 percent blind seed and 10-22 percent of samples had 70-100 percent diseased seed (Blair 1947). Stocks of seed throughout New Zealand had germination below 40 percent--in some ots as low as 5 percent (Osborn 1947). In seed exported from New Zealand to Ireland, 26 percent of samples had a low level of blind seed disease (Lafferty 1948).
Between 1948 and 1960, 70 percent of seed samples tested positive for blind seed disease; the average was 12 percent (Hampton and Scott 1980a). Levels of infection declined after 1960. During 1976-1978, 27 percent of samples tested positive, with a mean of 4 percent infected seed. The disease declined between 1964 and 1974 to the point that preharvest testing was stopped (Scott 1974). Hampton and Scott (1980a) related decreased levels of blind seed to the increased use of nitrogen fertilizers. In 1980-1990, only low levels of blind seed were detected (Skipp and Hampton 1996). In 1993, environmental conditions were favorable for blind seed development, and 100 percent of seed lots were infested, with a mean of 13.5 percent infected seed (Skipp and Hampton 1996). Low levels of blind seed infection returned in 1995 when conditions were again less favorable for blind seed development (Skipp and Hampton 1996).
Northern Ireland. By 1944, infection levels ranged from 31 to 55 percent and were as high as 70 percent in perennial ryegrass (Calvert and Muskett 1944). During 1947-1948, 60-70 percent of samples had trace to 60 percent infected seeds (Lafferty 1948).
United States. In the Willamette Valley of Oregon, low germination in ryegrass was first noticed in 1941 (Hardison 1957). Blind seed disease was positively identified in 1943 (Hardison 1948, 1949). By 1944, the disease was found in 85 percent of certified samples (Hardison 1945), and about one-quarter of the seed crop could not be certified (Hardison 1948).
U.S. levels of infection with blind seed disease declined during the late 1940s after the introduction of field burning to control the disease (Hardison 1976, Hardison 1980). During the 1950s, blind seed increased as growers explored alternatives to field burning. During the 1960s, when field burning was again widely practiced, blind seed occurrence returned to trace levels. Low levels of the disease were detected during 1986-1989 (Alderman 1991a,b).
In 1991, the Oregon State legislature mandated an incremental reduction in postharvest burning of grass fields to a maximum of 16,000 hectares after 1997. The area burned declined from about 80,000 hectares in 1987 to about 28,000 in 1993 (Young et al. 1994). In 1995, a high level of blind seed (20 percent infected seeds) was found in several fields of tall fescue in Oregon (Alderman 1996). However, surveys from 1995-1997 (Alderman 1999) indicate that blind seed disease levels in most fields in Oregon remain low.
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Original posting: October 2001.