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2007. Plant Management Network. This article is in the public domain.
Accepted for publication 9 July 2007. Published 23 October 2007.


Occurrence of Ustilago striiformis in Dactylis glomerata Seed Production Fields in Oregon


Steve C. Alderman, USDA-ARS National Forage Seed Production Research Center, Corvallis, OR 97331; Cynthia M. Ocamb, and Mark E. Mellbye, Oregon State University, Corvallis 97331; and Mohamed S. Sedegui, Oregon Department of Agriculture, Salem, OR 97301


Corresponding author: Steve Alderman. aldermas@onid.orst.edu


Alderman, S. C., Ocamb, C. M., and Sedegui, M. S. 2007. Occurrence of Ustilago striiformis in Dactylis glomerata seed production fields in Oregon. Online. Plant Health Progress doi:10.1094/PHP-2007-1023-01-RS.


Abstract

Stripe smut, caused by Ustilago striiformis, is a common disease of grasses grown for turf, but quantitative information concerning its occurrence in grass seed production fields is lacking. In 2004, 2005, and 2006, stripe smut was detected in 16, 17, and 3 out of 51, 42, and 33 Dactylis glomerata (orchardgrass) seed production fields surveyed in western Oregon, respectively. Stripe smut was not previously known to occur in these fields. The percentage of plants per transect with stripe smut in 2004, 2005, and 2006 ranged from 0 to 12, 0 to 4, and 0 to 1, respectively. In additional surveys during 2004-2006, to determine whether stripe smut was also occurring in seed production fields of other grasses in western Oregon, stripe smut was found in one field of Agrostis stolonifera, but was not detected in fields of Agrostis castellana, A. capillaries, Festuca arundinacea, F. longifolia, F. ovina, F. rubra subsp. commutata, F. rubra subsp. rubra, or Lolium perenne.


Introduction

While conducting disease surveys in Dactylis glomerata L. (orchardgrass) seed production fields in Oregon in 2003, stripe smut, caused by Ustilago striiformis (Westend.) Niessl was detected in six out of ten fields examined. Stripe smut was not previously known to occur in these fields. Fischer (7) lists U. striiformis on grasses in Oregon by 1935, but details on location and extent of occurrence are lacking. Hardison (10) reported the first appearance of stripe smut in seed production fields of Agrostis palustris Huds. ‘Pennlu’ and Poa pratensis L. ‘Merion’ in Oregon during the 1960s, but we are not aware of any reports of stripe smut in seed production fields of orchardgrass.

Fig. 1. Stripe smut on Dactylis glomerata.

 

Nearly all of the domestic orchardgrass seed is produced in the Willamette Valley in western Oregon. In 2005, orchardgrass was grown on 7,029 ha, with seed sales valued at $8.3 million (3). This included 3,454 ha (227 fields) of orchardgrass grown for certified seed (1). Stripe smut in orchardgrass could have a serious impact on both seed production and seed export.

Ustilago striiformis is an important pathogen of turf, especially Poa and Agrostis species (8,17) and can also cause significant damage in pastures (16). Over-wintering stripe smut spores germinate in the spring and infect seedlings through the coleoptiles, buds of crowns, or rhizome nodes (2,12,13,14). Characteristic symptoms include a shredded leaf appearance resulting from rupturing of long, dark-brown to black sori that develop between the leaf veins (Fig. 1). Ustilago striiformis has a wide host range (7), although formae speciales are known to occur (3,4,8), including one on D. glomerata (4).

The objectives of this study were to determine the incidence of stripe smut among and within in orchardgrass seed production fields in western Oregon, and to determine whether the disease may be present in seed production fields of other grass species in the Willamette Valley.


Stripe Smut Survey

During 2004, 2005, and 2006, 51, 42, and 33 fields, respectively, were examined. The same fields were surveyed each year, so a reduction in number of fields in consecutive years occurred as fields were taken out of orchardgrass seed production and planted with another crop. Fields were arbitrarily selected and included fields throughout the range of production in the Willamette Valley. The 51 fields selected represented about 20% of the total orchardgrass certified seed production fields. Within each field, the number of plants with and without stripe smut symptoms were counted in each of 10 arbitrarily selected 1-m row length sections, approximately equally spaced along each of 4 transects arranged in a diamond pattern. Each plant with presumed stripe smut was placed in an individual paper bag and brought to the lab for examination. Spores from each infected plant were examined in water at 400 Χ for size, shape, color, and echinulation pattern to verify identity of U. striiformis, as described by Fischer (7).

Fields of other seed production grasses were arbitrarily selected and surveyed as described above for stripe smut. The grass species and number of fields examined for each species during 2004-2006 are listed in Table 1.


Table 1. Occurrence of Ustilago striiformis during 2004–2006 in various species of grasses grown for seed in Oregon.

Grass species Fields with U. striiformis / fields examined
2004 2005 2006
Agrostis castellana 0 / 8   0 / 10 0 / 7
Agrostis stolonifera 0 / 4   0 / 13   1 / 12
Agrostis capillaris 0 / 1 — —
Dactylis glomerata 16 / 51  17 / 42     3 / 33
Festuca arundinacea  0 / 22   0 / 29   0 / 27
F. longifolia 0 / 1 0 / 1 0 / 1
F. ovina — 0 / 1 0 / 1
F. rubra subsp. commutate  0 / 14   0 / 12 0 / 7
F. rubra subsp. rubra 0 / 6 0 / 8 0 / 6
Lolium perenne  0 / 24   0 / 21   0 / 15

In 2004, 2005, and 2006, stripe smut was found in 16, 17, and 3 out of 51, 42, and 33 orchardgrass fields, respectively (Table 1). No other smut fungi were detected in the surveyed fields. The 51 fields sampled in 2004 represented about 20% of the fields grown for certified seed and included 22 cultivars, of which 12 cultivars were found with stripe smut. In a survey for stripe smut in seed production fields of other grasses, the disease was found in one field of Agrostis stolonifera in 2006. Otherwise, stripe smut was not found in fields of Agrostis castellana, A. capillaries, Festuca arundinacea, F. longifolia, F. ovina, F. rubra subsp. commutata, F. rubra subsp. rubra, or Lolium perenne (Table 1).

The percentage of plants per transect with stripe smut in 2004, 2005, and 2006 ranged from 0 to 11.7, 0 to 3.8, and 0 to 1.3, respectively (Table 2). In 2006, both reduction in number of fields with stripe smut and percentage of infected plants were observed. Within fields, among the 40 sample sites per field (with each site including 1 m row length), zero to two infected plants per meter row length were typical, but clusters of 3 or 4 plants/m were found in four fields in 2004 and two fields in 2005. (Fig. 2). A meter of row length included five to seven plants.


 

Fig. 2. Frequency of occurrence of plants per meter row length infected with Ustilago striiformis in 16 Dactylis glomerata seed production fields in 2004 and 2005. Field numbers correspond to those in Table 2.

 

Table 2. Mean ± standard deviation of percentage plants per transect with Ustilago striiformis among 22 fields of orchardgrass in 2004-2006. An "—" indicates that the field was taken out of production and replanted with another crop.

Field Mean ± standard deviation
percentage plants per transect with U. striiformis
2004 2005 2006
1 11.7 ± 4.6 3.8 ± 6.7 1.3 ± 2.7
2 11.2 ± 3.5 2.9 ± 0.8 0.7 ± 1.4
3 8.2 ± 9.1 1.2 ± 1.5 —
4 3.9 ± 4.4 3.5 ± 1.5 1.2 ± 2.4
5 2.2 ± 1.9 — —
6 2.2 ± 3.3 — —
7 1.7 ± 2.5 2.2 ± 2.6 0
8 1.3 ± 2.7 4.8 ± 2.2 0
9 0.9 ± 1.0 1.0 ± 2.0 —
10 0.7 ± 0.9 1.2 ± 1.4 0
11 0.6 ± 1.2 — —
12 0.4 ± 0.9 0 0
13 0.3 ± 0.6 1.1 ± 2.3 —
14 0.3 ± 0.6 — —
15 0.4 ± 0.9 1.3 ± 2.6 0
16 0.4 ± 0.8 0.5 ± 1.1 0
17 0 0.8 ± 1.7 —
26 0 0.9 ± 1.1 0
27 0 0.7 ± 1.4 0
30 0 1.0 ± 1.1 —
33 0 2.4 ± 2.1 —
40 0 0.4 ± 0.8 0

In 2004, fields with stripe smut were located in the eastern Benton and western Linn counties, where the two counties are separated by the Willamette River (Fig. 3). In 2005, stripe smut was also found in one field in Marion Co. and one field in Yamhill Co. (Fig. 3). In 2006, the three fields with stripe smut were located in only eastern Benton and western Linn counties.


 

Fig. 3. Distribution of field with (x) and without (o) Ustilago striiformis in orchardgrass seed production fields in 2004 and 2005.

 

Discussion and Options for Stripe Smut Management

The report of Fischer (7) of the occurrence of U. striiformis in orchardgrass suggests that the fungus has apparently been in the Willamette Valley since at least 1935, when Fischer’s Manual of North American Smut Fungi was published. It is not clear whether U. striiformis has simply gone undetected in orchardgrass seed production fields or whether the appearance of stripe smut in orchardgrass is a recent occurrence. It is possible that changes in post harvest residue management initiated during the 1990s may have resulted in conditions favorable for U. striiformis. For many years, fields were burned post harvest to eliminate the leaf and straw residues and for disease and pest control. Legislation in 1991 limited hectarage burned to 16,187 annually for grasses grown for seed in the Willamette Valley. As a consequence, few of the orchardgrass fields have been burned since 1991. Hardison (11) reported partial control of stripe smut in bluegrasses in Oregon during the 1950s by post harvest open field burning. Although open field burning of post harvest straw residues would destroy overwintering spores within leaf residues consumed by the fire, U. striiformis systemically infecting crown tissues would likely escape the high temperature effects or burning.

Our observation that stripe smut was confined primarily to orchardgrass suggests the possibility of the occurrence in Oregon of an orchardgrass specific forma specialis of U. striiformis. Davis (4) reported finding a forma specialis of U. striiformis in orchardgrass from New York that had a host range restricted to orchardgrass. He considered it a separate species of Ustilago (U. clintoniana), based primarily on host range, but this was refuted by Fischer (7).

It is not clear why few fields were found with stripe smut in 2006. A reduction in infected plants could have resulted from conditions unfavorable for survival during prolonged dry conditions during the summer/fall of 2005, or dry conditions during the early spring of 2006. Despite the reduction in stripe smut in 2006, the incidence and severity of the disease in 2004 and 2005 is of concern. Consecutive years favorable for U. striiformis could be potentially significant in orchardgrass seed production, given the widespread occurrence of the pathogen among fields within the production area.

Grass seed production in Oregon currently does not include control or management of U. striiformis. Cultural controls of U. striiformis in orchardgrass seed production fields have not been established, and it is not known whether resistance to U. striiformis occurs among orchardgrass cultivars. Studies in wheat suggest that grazing may reduce the severity of smut (6). In Oregon, some orchardgrass seed production fields are grazed by sheep during the late fall through early spring, although the effect of sheep on U. striiformis development in orchardgrass seed production fields is not known.

Stripe smut was found on 12 of 22 cultivars included in the survey. It is not known whether any of the orchardgrass cultivars currently grown have any resistance to infection by U. striiformis. Disease resistance has been noted in cultivars of Poa pratensis (9,15), but we are not aware of any studies to evaluate U. striiformis resistance in orchardgrass.

An estimate of the impact of smut on export of orchard grass was derived from data published by the USDA Foreign Agricultural Service (USDA FAS) and records of the Oregon Department of Agriculture. The USDA FAS maintains market and trade data reports online. According to the US planting seed report, 4 June 2007, 302 metric tons of orchard grass seed were exported between July 2005 and March 2006, with an export value of $1.3 million. In 2003, 2004, 2005, and 2006, the Oregon Department of Agriculture detected smut spores (Ustilago spp.) in 7.8, 5.7, 12.4, and 4.5% of seed lots examined for export. We are not aware of any species of Ustilago other than U. striiformis in orchard grass seed production fields during 2003-2006.

Although U. striiformis is widespread within the US, the distribution and planting of orchardgrass with spores of U. striiformis is of concern. Currently, orchardgrass growers do not test or treat seed for smut. The potential impact of stripe smut on orchard grass seed production and export warrents smut testing of seed used to establish seed fields in the Willamette Valley, and treatment of infested seed would be prudent. Post-harvest open field burning, removal of residues through post-harvest baling, baling followed by propane burning, or winter grazing with sheep are viable options for at least partial smut control that could be included in stripe smut control trials in perennial seed production fields of orchardgrass.


Acknowledgment

We thank Barbara Matson for technical assistance with the field surveys.


Literature Cited

1. Anonymous. 2005. Oregon Certification Activity Summary, 2005. Oregon Seed Certification Office Spec. rep. 05-004, Oregon State Univ. Ext. Serv., Corvallis, OR.

2. Davis, W. H. 1926. Life history of Ustilago striaeformis (Westd.) Niessl which causes a leaf smut in timothy. J. Agric. Res. 32:69-76.

3. Davis, W. H. 1930. Two physiologic forms of Ustilago striaeformis (Westd.) Niessl. Phytopathology 20:65-74.

4. Davis, W. H. 1935. Summary of investigations with Ustilago striaeformis parasitizing some common grasses. Phytopathology 25:810-817.

5. Extension Economic Information Office. 2005. Oregon county and state agricultural estimates. Spec. rep. 790-05, Oregon State Univ. Ext. Serv., Corvallis, OR.

6. Finnell, H. H. 1929. Relations of grazing to wheat smut and tillering. J. Am. Soc. Agron. 21:367-374.

7. Fischer, G. W. 1935. Manual of the North American Smut Fungi. The Ronald Press, New York, NY.

8. Fischer, G. W. 1940. Fundamental studies on the stripe smut of grasses (Ustilago striaeformis) in the Pacific Northwest. Pytopathology 30:93-118

9. Halisky, P. M., Funk, C. R., and Bachelder, S. 1966. Stripe smut of turf and forage grasses: Its prevalence, pathogenicity, and response to management practices. Plant Dis. Reptr. 50:294-298.

10. Hardison, J. R. 1966. Chemotherapeutic control of stripe smut (Ustilago striiformis in grasses by two derivatives of 1,4-Oxathiin. Phytopathology 57:242-245.

11. Hardison, J. R. 1980. Role of fire for disease control in grass seed production. Plant Dis. 64:641-645.

12. Hodges, C. F. 1976. Comparative primary infection characteristics of Ustilago striiformis and Urocystis agropyri on cultivars of Poa pratensis. Phytopathology 66:1111-1115.

13. Hodges, C. F., and Britton, M. P. 1970. Directional growth and the perennial characteristic of Ustilago striiformis in Poa pratensis. Phytopathology 60:849-851.

14. Hodges, C. F., and Britton, M. P. 1968. Infection of Merion bluegrass, Poa pratensis, by stripe smut Ustilago striiformis. Phytopathology 59:301-304.

15. Kreitlow, K. W., and Juska, F. V. 1959. Susceptibility of Merion and other Kentucky bluegrass varieties to stripe smut (Ustilago stiiformis). Agron. J. 51:596-597.

16. Kreitlow, K. W., and Myers, W. M. 1944. Prevalence and distribution of stripe smut of Poa pratensis in some pastures of Pennsylvania. Phytopathology 34:411-415.

17. Smith, J. D., Jackson, N., and Woolhouse, A. R. 1989. Fungal Diseases of Amenity Turf Grasses, 3rd Ed. E. & F. N. Spon, New York, NY.