Stem rust (Puccinia graminis). The first report of barley stem rust in 1999 was in early July in west central Minnesota disease detection plots, where traces of stem rust were found on the 2-row barley cultivar Hypana. By early July, trace to 50% severities were reported on 6-rowed barley in a north central South Dakota field. By mid-July, traces of stem rust were common on both 2- and 6-rowed barleys growing in plots and in fields in the southern area of the Red Valley of the North. In late July, 40% severities were observed in plots in northeastern North Dakota and traces in plots in northeastern Montana. Most of these barley rust infections were probably due to stem rust race QCCJ which infects barley. QCCJ was identified from collections made from wheat in May in two nurseries in Texas and one in Louisiana. Overall the number of isolates of stem rust identified at the CDL in 1999 was nearly triple that in 1997 and double that in 1998. As a result there appears to be an increase in the overwintering of race QCCJ from its very low level in 1997 (no collections identified as QCCJ at the CDL). While stem rust development on barley was more significant in 1999 than in recent years, losses were still light (Table 2).

In mid-July, trace to 10% stem rust severities were reported on wild barley (Hordeum jubatum) plants growing alongside the roadway in eastern South Dakota. This was the most extensive stem rust observed on wild barley in this area in the last 5 years.

In 1999, race QCCJ comprised 83% (117 isolates) of the total isolates identified from barley (Table 1), an increase from 23% (3 isolates) in 1998. QCCJ comprised 65, 90, 94, 87, 56, and 81% of the isolates from 1989 to 1994, respectively. The percentage of isolates of QCCJ identified declined from 89 to 14,and 0%, from 1995 through 1997, respectively. The second most common race identified from barley in 1999 (6% of total isolates identified from barley) was RCRS which comprised 46% of the total race population in 1998. Barley stem rust was only found in the northern Great Plains in 1999 and losses to barley stem rust were generally light but there were some significant losses in late planted fields in South and North Dakota (Table 2).

 Leaf rust (Puccinia hordei). Traces of leaf rust were observed on lower leaves in a few barley plots in southern Texas in mid-March. In late April, traces of barley leaf rust were found on cultivars growing in nurseries in central Texas.

In early April, leaf rust severities from 25-50% were reported on susceptible winter barleys in Maryland. Leaf rust severities from trace to 15% were found in plots of winter barley in Virginia in mid-May.

In early May, traces of barley leaf rust were found in the Skagit Valley of western Washington. During late May, barley leaf rust was increasing on the winter barleys and traces were found on the spring barleys in northwestern Washington. Barley leaf rust severities of 50% were reported on susceptible winter barleys in western Washington and rust was just starting to increase on spring barleys during the third week in June. No barley leaf rust was reported in eastern Washington in 1999.

In late June, severities of 20% were reported on the lower leaves in spring barley plots in east central Nebraska and traces were found in plots in west central Minnesota. Trace to 10% leaf rust severities were observed in barley plots in south central Minnesota, east central South Dakota and southeastern North Dakota in mid-July.

Twelve differential barley genotypes were used to identify races of P. hordei (Table 3). These races were designated according to a system similar to that of Roelfs and Martens (Phytopathology 78:526-533) as shown in Table 4. Nine races of barley leaf rust were identified from 23 viable collections in 1999 (Table 5). The most common were race RFD (26%, Maryland, Ohio and Virginia), RCD (26%, Nebraska, North Dakota, Ohio and Virginia) and MCD (22%, Maryland, Minnesota, North Dakota, and South Dakota). As in the past, virulence to Rph1, 2, 4, 8, and 11 was common, while virulence to Rph3, 5, 9, and 12 was absent. However, virulence to Rph7, which had not been seen since 1990, was common in 1999 in the eastern U.S. (Maryland, Ohio, Virginia).

With the exception of North Carolina, where a 6% loss to barley leaf rust occurred, losses to barley leaf rust were generally light in the U.S. in 1999 (Table 2).

Stripe rust (Puccinia striiformis). Barley stripe rust severities of 80-100% were reported in susceptible plots on the University of California-Davis agronomy farm in mid-April. By early May, barley stripe rust was observed in nurseries in the Sacramento and San Joaquin Valleys of California at severities of 80-100% with lesser severities in fields. A barley loss of 16%, due to stripe rust, was reported in California in 1999 (Table 2).

In mid-April, severities of less than 1% were noted on barley lines in the Skagit Valley nursery of western Washington. Cooler than normal conditions delayed crop maturity and rust development. By the third week in May, foci of stripe rust were found in barley plots at Corvallis, Oregon. By mid-June, in western Washington, 30% severities were observed on susceptible barley cultivars, while in eastern Washington no stripe rust on barley was found. The dry fall and cool dry May, which is the critical month for rust development, were not conducive for the disease. In late June, barley stripe rust was increasing on susceptible cultivars in western Washington, while only traces were found in plots in eastern Washington. By mid-July, stripe rust on barley was increasing in the Pacific Northwest, but there was much less rust than in 1998. Barley losses due to stripe rust were significantly less than 1998 in the Pacific Northwest (Table 2).

Barley stripe rust was virtually non-existent in Idaho this year with the exception of a severely diseased field of spring barley in eastern Idaho. In early July, trace amounts of stripe rust were reported in the Bozeman area of Montana.

Crown rust on barley. Moderate levels of aecial infection were observed on buckthorn in the barley crown rust nursery in Fargo, North Dakota, the week of May 24. In mid-June, infection on barley was light. By late July, crown rust was severe on barley in plots at Fargo. In mid-June, a few pustules of barley crown rust were seen on winter rye in southeastern South Dakota plots.