Losses to barley stem rust were light in 1997 (Table 1).

Leaf rust (Puccinia hordei). During the first week in April, leaf rust severities of trace to 10% were observed on the lower leaves of barley in southern and central Texas plots. Trace rust severities were observed in barley plots in the Southern San Joaquin Valley of California (Merced County) and in the Yuma, Arizona area. Rust severities from 10-40% developed on barley in this region of California by mid-May and in Virginia, traces of leaf rust were found in barley nurseries.

In late May, light amounts of barley leaf rust were reported in south central Pennsylvania and in the Skagit Valley of western Washington on winter barleys. By the second week in June, barley leaf rust was moderate to severe, and in early July, it was severe on susceptible fall-planted and spring-planted cultivars in the varietal plots in the Skagit Valley.

In mid-July, leaf rust severities of trace to 40% were observed in barley plots in west central Minnesota and northeastern South Dakota; however, no leaf rust was found in commercial fields. Leaf rust developed relatively late on barley in North Dakota. In mid-August, leaf rust severities ranged from trace to 25% in commercial fields in north central North Dakota. At Langdon, some late maturing lines had a rust severity of 60% in early September.

Twelve differential barley genotypes were used to identify races of P. hordei (Table 2). These races were designated according to a system similar to that of Roelfs and Martens (Phytopathology 78:526-533) as shown in Table 3. Ten races of barley leaf rust were identified from 24 collections in 1997 (Table 4). The most common races were race RHD (20%, Arizona and North Dakota), MCD (20%, California, North Dakota, and Virginia), and MCJ (14%, North Dakota). These results are similar to those observed in 1996, where races RHD and MCJ were most common.

In 1997, losses to barley leaf rust were light in the U.S. (Table 1).

Stripe rust (Puccinia striiformis f. sp. hordei). In early March, ôhot spots ô of barley stripe rust were observed in nurseries and variety strip tests on the UC Davis agronomy farm in Davis California. By the first week of April, barley stripe rust was severe on the Davis campus and Yolo county plots in California. During the second week in April, barley stripe rust was present in light to severe amounts in commercial fields in the San Joaquin Valley of California. In some fields, the infections were lighter than in 1996, but in other fields, 20% severities were observed on flag leaves. Barley stripe rust appeared to increase even under dry conditions. During late April, barley stripe rust was widespread in CaliforniaÆs fall-sown spring barley crop. Some advanced lines that exhibited low rust severities last season were susceptible in 1997. Many of the commercial cultivars are extremely susceptible to stripe rust, while UC 603 exhibited a high level of tolerance. By early July, stripe rust on barley was appearing on spring-sown barley in the intermountain area of northeastern California. Severities of 80-100% were reported in northeastern California nurseries, and in commercial fields 100% severities were reported on flag leaves at the milk stage of development. Many fields in this area were sprayed with Folicur to control the rust. Except for northeastern California, total crop damage was less than in 1996, since stripe rust onset was late this season and crop development was earlier.

In early March, barley stripe rust was found in winter barley plots at Corvallis, Oregon. By late March, stripe rust pustules were found at low levels in susceptible cultivars within a 16 m diameter circle of the original infected plots, and by mid-April, barley was heavily infected with stripe rust in winter trial plots at Corvallis. During the last two weeks of April, cool, wet weather slowed stripe rust development in winter barley plots, but in late May, barley stripe rust was increasing in spring barley plots at Corvallis.

In late April, stripe rust severities of 20% were reported on the lower leaves of winter barley growing in the Skagit Valley of western Washington, and by late May the rust was severe. By the first week in July, barley stripe rust was severe on susceptible fall-planted and spring-planted cultivars growing in varietal plots in the Skagit Valley. In early July, light amounts of barley stripe rust were detected in the Palouse region of Washington and Idaho.

In mid-July, severities of 70% were observed in spring barley test plots in west central Idaho, while traces were found in the northern tip of Idaho. Since the plants were in an advanced plant growth stage, the rust did not significantly affect the yield.

Barley stripe rust is now firmly established in California and the Pacific Northwest, where the climate is most favorable for its development. Losses to barley stripe rust occurred in fields throughout California and the Pacific Northwest. In 1997, 20, 4, 0.5 and 0.1% losses to barley stripe rust occurred in California, Oregon, Washington and Idaho, respectively (Table 1).

Crown rust (Puccinia coronata). In mid-June, crown rust severities of up to 15% were observed on barley lines growing 15 meters from Rhamnus plants in a nursery at Casselton, North Dakota. Barley crown rust was found in several commercial fields in trace amounts in the Red River Valley region in mid-August. Crown rust reached 80% severity on susceptible barley cultivars planted in an east central South Dakota nursery. Losses in barley to crown rust were negligible in 1997.
 

Table 1. Estimated losses in barley due to rust in 1997

					Losses due to
	1000	Yield in	Production,	Stem	Rust	Leaf	Rust	Stripe Rust
	acres	bushels	1000		1000		1000		1000
State	harvested	per acre	bushels	%	bushels	%	bushels	%	bushels
AZ	67	102.5	6,834	0	0	0	0	0	0
CA	180	55	9,900	0	0	1	125	20	2506
CO	90	112	10,080	0	0	*T	T	0	0
ID	760	79	60,040	0	0	0.1	60	0.1	60
KS	8	40	320	0	0	0	0
KY	14	75	1,050	0	0	T	T
MI	24	60	1,440	0	0	0	0
MN	540	51	27,540	T	T	T	T
MT	1,200	53	63,600	0	0	0	0	0	0
NE	8	51	408	0	0	0	0
NC	20	70	1,400	0	0	5	74
ND	2,250	45	101,250	T	T	T	T
OK	8	42	336	0	0	0	0
OR	120	69	8,280	0.1	9	2	176	4	353
PA	75	68	5,100	0	0	T	T
SC	3	60	180	0	0	1	2
SD	130	38	4,940	T	T	T	T
TX	5	47	235	0	0	0	0	0	0
UT	95	86	8,170	0	0	0	0
VA	65	85	5,525	0	0	T	T
WA	490	76	37,240	0.2	75	0.1	38	0.5	188
WI	65	55	3,575	0	0	0	0
WY	115	80	9,200	0	0	0	0
Total	6,332		366,643		75		475		3107
Average		57.9		0.02		0.13		0.84
U.S.	6,425	58.3	374,478
*T = Trace

Table 2. Barley genotypes used to differentiate isolates of Puccinia hordei

Genotype	Resistance gene(s)
Sudan	Rph1
Peruvian	Rph2
Estate	Rph3
Gold	Rph4
Magnif	Rph5
Bolivia	Rph6+2
Cebada Capa	Rph7
Egypt 4	Rph8
Hor 2596	Rph9
Clip BC8	Rph10
Clip BC67	Rph11
Triumph	Rph12

 

Table 3. A proposed North American system of pathotype nomenclature for Puccinia hordei based on 12 differential barley hosts^a Infection phenotype of pathogen and barley Rph genes

Set 1	Rph1	Rph2	Rph3	Rph4
Set 2	Rph5	Rph6+2	Rph7	Rph8
Set 3	Rph9	Rph10	Rph11	Rph12
Ph-code
B	Low	Low	Low	Low
C	Low	Low	Low	High
D	Low	Low	High	Low
F	Low	Low	High	High
G	Low	High	Low	Low
H	Low	High	Low	High
J	Low	High	High	Low
K	Low	High	High	High
L	High	Low	Low	Low
M	High	Low	Low	High
N	High	Low	High	Low
P	High	Low	High	High
Q	High	High	Low	Low
R	High	High	Low	High
S	High	High	High	Low
T	High	High	High	High

^a Pathotype designations are based on the infection phenotypes of the pathogen isolate on the 12 differential barley hosts. Low = incompatibility (infection phenotypes 0, 0;, 1, or 2) and High = compatibility (infection phenotypes 3 or 4). The infection phenotypes from set 1 determine the first letter of the code, those from set 2 the second letter, etc.
 

Table 4. Races of Puccinia hordei identified from the United States in 1997

	Number of
State	collections	Source	Pathotypes and (number of collections)
Arizona	1	Nursery	RHD(1)
Arkansas	1	Nursery
California	5	Nursery	RHB(1), RCB(1), RBB(1),MBD(1), MCD(1)
Minnesota	3	Nursery	RHJ(1)
North Dakota	8	Field	MCJ(2), RHD(2), MBB(1), MCD(1)
Pennsylvania	1	Field
South Dakota	3	Nursery	MHD(1)
Tennesee	1	Field
Virginia	1	Nursery	MCD(1)
TOTAL	15 a

a - nine collections produced no infection and were classified as dead.