Cause Puccinia striiformis, a fungus that overwinters on infected plants. In the Willamette Valley, stripe rust is a serious disease in bluegrass. It also attacks orchardgrass. An alternate host for stripe rust is unknown. This population of stripe rust does not attack wheat, or vice versa. In spring, primary infection is from windborne urediniospores produced on infected plants. Secondary spread continues from subsequent infections. As the season passes, urediniospore production drops or ceases; black teliospores are produced instead.
On bluegrass, the disease may develop rapidly when free moisture (rain or dew) occurs and temperatures range between 50°F and 55°F. Nearly every year it can be found as early as January or February.
On orchardgrass, the disease is most serious when free water is present and temperatures are 70°F to 75°F. In most years, stripe rust is not epidemic in orchardgrass because higher temperatures are required for growth and increase. However, in low spots in a field or during early warm weather, the disease can be serious.
Symptoms Pustules contain yellow to orange-yellow urediniospores that form in narrow, linear stripes on leaves' upper sides. Pustules also are on stems, the leaf sheath, and the outer and inner side of the glumes.
Chemical control Spray dates may vary due to yearly variations in rain and temperatures. Applications at flag leaf emergence, even if rusts are not visible, can help in a year when rust does not develop fully due to low temperatures.
Kentucky bluegrass-one (1) to three (3) applications for stripe rust control beginning about April 15 to 20.
Although there are no documented fungicide-resistant rusts in grass seed fields, rotating fungicides with different modes of action may reduce the potential for resistance to develop. There are now fungicides labeled that provide an effective rotation program.
- Chlorothalonil products (Group M5) such as:
- Bravo Ultrex at 0.9 to 1.4 lb/A on 14-day intervals. Do not apply within 14 days of harvest. Do not allow livestock to graze in treated areas or feed treated plant parts to livestock. 12-hr reentry.
- Echo 720 at 1 to 1.5 pints/A or Echo 90DF at 0.875 to 1.25 lb/A at 14-day intervals. Do not apply within 14 days of harvest. Do not allow livestock to graze in treated areas or feed treated plant parts to livestock before harvest. 12-hr reentry.
- Demethylation-inhibiting (DMI) fungicides (Group 3) are labeled for use.
- Bumper 41.8 EC at 4 to 8 fl oz/A (maximum 4 fl oz on bluegrass) in a minimum of 20 gal water/A for ground application or 10 gal water/A for air application on 14- to 21-day intervals. Make last application 20 days before seed matures. Do not feed cut hay within 20 days of last application nor graze treated areas within 140 days of the last application. 12-hr reentry.
- Muscle 3.6 F at 4 to 8 fl oz/A on 14- to 16-day intervals. 12-hr reentry.
- PropiMax EC at 4 to 8 fl oz/A (except bluegrass apply 4 fl oz/A) on 14- to 21-day intervals. Make the last application at least 20 days before seed matures. Do not feed hay cut within 20 days of the last application. Do not graze treated areas within 140 days of the last application. 12-hr reentry.
- Rally 40WSP at 5 to 7 oz/A in a minimum of 10 gal of water on 14- to 21-day intervals. Oregon only (SLN OR-090006). Do not use within one year of harvesting grass hay, grazing of the field. No portion of the treated field, including seed, seed screenings, hay forage or stubble may be used for human or animal feed. 24-hr reentry.
- Tebustar 3.6L at 4 to 8 fl oz/A on 14- to 16-day intervals. Preharvest interval is 4 days. Chaff, screenings, and straw from treated areas may be used for feed purposes. Regrowth may be grazed 17 days after last application. 12-hr reentry.
- Tilt at 4 to 8 oz/A (maximum 4 oz on bluegrass) when infection is noticeable and increasing in number, in late spring or early summer. Repeat on 14- to 21-day intervals. Last application at least 20 days before seed matures. Preharvest for hay is 20 days; do not graze within 140 days after last application. 12-hr reentry.
- Toledo at 4 to 8 fl oz/A on 14- to 16-day intervals. Do not apply within 4 days of harvest. Do not forage or cut green crop for feed purposes. Chaff, screenings, and straw from treated areas may be used for feed purposes. Regrowth may be grazed starting 17 days after the last application. 12-hr reentry.
- JMS Stylet Oil at 1 to 2 gal/A. Slightly effective when used alone but most effective when tank-mixed with Tilt at 4 to 6 oz/A. Do not spray when freezing temperatures are anticipated within 48 hr of an oil application, when temperature is above 90°F, or when plants are wet or under heat or moisture stress. Spray with at least 20 gal/A water. 4-hr reentry. O
- Regalia 12 (Group P5) at 13.33 to 53.33 fl oz/A on 7-day intervals. Does not benefit from the addition of an adjuvant. Preharvest interval is 0 days. 4-hr reentry. O
- Strobilurin fungicides (Group 11) are labeled for use. Do not make more than two (2) applications of any Group 11 fungicide before alternating to a labeled fungicide with a different mode of action.
- Abound at 6 to 15.5 fl oz/A on 10- to 14-day intervals. May be applied up to 8 days before swathing. 4-hr reentry.
- Absolute 500 SC at 5 to 7.7 fl oz/A on 21-day intervals. Do not apply within 4 days of harvest. Do not forage or cut green crop for feed purposes. Chaff, screenings, and straw from treated areas may be used for feed purposes. Regrowth may be grazed starting 17 days after the last application. 12-hr reentry.
- Headline at 6 to 12 fl oz/A. First application should be at the flag leaf stage or at the early onset of disease. Make a second application 14 to 21 days later. Do not graze or feed forage or hay to livestock within 27 days of last application. Preharvest interval is 14 days. 12-hr reentry.
- Premixes of fungicides are available for use.
- Quilt (Group 3 + 11) at 14 to 27.5 fl oz/A (except bluegrass apply at 14 fl oz/A) or Quilt Xcel (Group 3 + 11) at 14 to 26 fl oz/A on 14-day intervals; not labeled for bermudagrass grown for seed. Make the last application at least 20 days before seed matures. Do not feed hay cut within 20 days of the last application. Do not graze treated areas within 140 days of the last application. For use in Oregon, Washington, Idaho, Minnesota, and Nebraska only. 12-hr reentry.
- Trivapro (Group 3 + 7 + 11) at 13.7 to 27.4 fl oz/A on 14- to 28-day intervals. Do not make more than two (2) sequential applications of Trivapro or other Group 7 or Group 11 fungicides. Preharvest interval is 20 days. 12-hr reentry.