Spore production appears to be ramping up in the Lower Columbia Basin of Oregon:

Accumulated degree-days as of May 20 were 539 in Hermiston, OR (orange line). According to the model, most ascospores are produced in the Lower Columbia Basin when accumulated degree-days are between 414 and 727.
At this time in 2019, accumulated degree-days were 482 (dotted line).

This research is funded by the Washington Turfgrass Seed Commission, the Oregon Seed Council, the Eastern Oregon Kentucky Bluegrass Working Group, and the Oregon Department of Agriculture Alternatives for Field Burning Research Financial Assistance Program.

Updated spore counts are available for the central Oregon area:

  • It is recommended that growers scout fields as grass seed crops approach anthesis.
  • Protective fungicides should be applied prior to the onset of anthesis to protect unfertilized flowers from infection.
  • Cultivars with prolonged flowering periods may require multiple applications.
  • Please refer to the PNW Plant Disease Management Handbook for more information (https://pnwhandbooks.org/plantdisease/host-disease/grass-seed-ergot).

This research is funded by the Washington Turfgrass Seed Commission, the Oregon Seed Council, the Eastern Oregon Kentucky Bluegrass Working Group, and the Oregon Department of Agriculture Alternatives for Field Burning Research Financial Assistance Program.

Updated spore counts are available for the Grande Ronde Valley. Large numbers of spores were intermittently detected at the site:

*Figure updated on 5/21/20 to reflect the average number of cells per ascospore (Tiffany 1948).
  • It is recommended that growers scout fields as grass seed crops approach anthesis.
  • Protective fungicides should be applied prior to the onset of anthesis to protect unfertilized flowers from infection.
  • Cultivars with prolonged flowering periods may require multiple applications.
  • Please refer to the PNW Plant Disease Management Handbook for more information (https://pnwhandbooks.org/plantdisease/host-disease/grass-seed-ergot).

This research is funded by the Washington Turfgrass Seed Commission, the Oregon Seed Council, the Eastern Oregon Kentucky Bluegrass Working Group, and the Oregon Department of Agriculture Alternatives for Field Burning Research Financial Assistance Program.

Spore traps have detected the presence of airborne ergot ascospores around Kentucky bluegrass production areas in the Grande Ronde Valley.

*Figure updated on 5/21/20 to reflect the average number of cells per ascospore (Tiffany 1948).

Spore counts are relatively low and sporadic compared to other sites. However, a relatively few number of ascospores can begin an infection, and the honeydew (secondary) stage of the disease can amplify the disease in a field before harvest. Our research has shown that, at least in some cases, up to 30% of infections can be caused by honeydew.

It is also important to note that the spore traps currently being used at all sites sample a relatively small volume of air (about 3,800 gallons of air/day). Consequently, the ascospores that are detected and reported likely represent a small proportion of the total number in the area.

Spore trap results confirmed the presence of airborne ergot ascospores in the Lower Columbia Basin of Oregon (top) and Washington (bottom):

Spore counts in the Lower Columbia Basin of OR increased 6.8X during the week of May 4 – May 10 compared to April 27 – May 3.
*Figure updated on 5/21/20 to reflect the average number of cells per ascospore (Tiffany 1948).
A large spike of spores were observed on May 4 in the Lower Columbia Basin of WA.
*Figure updated on 5/21/20 to reflect the average number of cells per ascospore (Tiffany 1948).

The spore counts presented above are intended to show daily trends in spore production in their respective areas and do not necessarily indicate inoculum pressure in your field(s). Spore production can vary from field to field, and inoculum pressure tends to be higher in older fields with a history of ergot in the previous season, or in new fields planted next to established fields with a history of ergot.

A predictive model for ergot ascospores was developed for the Lower Columbia Basin of Oregon that uses accumulated degree-days (beginning January 1, with a base temperature of 50°F and upper threshold temperature of 77°F) to forecast when ascospores are likely to be present.

Accumulated degree-days as of May 10 were 435 in Hermiston, OR (orange line). According to the model, most ascospores are produced in the Lower Columbia Basin when accumulated degree-days are between 414 and 727.

At this time in 2019, accumulated degree-days were 365 (dotted line).

Spore trap results confirmed the presence of airborne ascospores in sentinal plots located at COAREC. A large number of spores were captured on the first day of trapping.

*Figure updated on 5/21/20 to reflect the average number of cells per ascospore (Tiffany 1948).

The cool, wet weather that is predicted for central Oregon over the next few days will likely be conducive to sclerotia germination and spore release. In general, ascospore production by the pathogen is favored by:

  • moderate temperatures (between 50°F and 80°F)
  • high soil moisture, rainfall, and/or irrigation.
  • conditions that delay or interfere with pollination, such as cool wet weather, can increase the period of susceptibility in grass seed crops.

It is recommended that growers scout fields as grass seed crops approach flowering (anthesis). Protective fungicides should be applied prior to the onset of anthesis to protect unfertilized flowers from infection, and cultivars with prolonged flowering periods may require multiple applications.

Please refer to the PNW Plant Disease Management Handbook for more information (https://pnwhandbooks.org/plantdisease/host-disease/grass-seed-ergot).

Germinating sclerotia were observed at several research sites in the Hermiston, OR area today. Grass seed growers and crop consultants can assume that ergot spores are currently present in the area.

Perennial ryegrass varieties are not yet flowering and susceptible to ergot, but earlier-flowering cultivars of Kentucky bluegrass may be ready for a fungicide application if ergot is a concern in your area.

Early-(left), middle-(center), and late-(right) maturing cultivars of Kentucky bluegrass at the OSU Hermiston Agricultural Research and Extension Center. Cultivars that are entering anthesis may be prone to ergot infection.

For maximum ergot control, fungicide applications should be timed to occur at the beginning of or immediately prior to flowering. Cultivars with long flowering periods may require (an) additional application(s).

More information on fungicide options for ergot in the Pacific Northwest can be found in the Pacific Northwest Disease Management Handbook: https://pnwhandbooks.org/plantdisease/host-disease/grass-seed-ergot .

Acknowledgement: This research is funded by the Eastern Oregon Kentucky Bluegrass Working Group, the Jefferson County Seed Growers Association, the Oregon Department of Agriculture Alternatives for Field Burning Research Financial Assistance Program, the Oregon Seed Council, the Union County Seed Growers Association, and the Washington Turfgrass Seed Commission.