Honeydew has been observed in non-treated, artificially-infested plots at the Hermiston Agricultural Research and Extension Center.

In contrast to airborne ascospores, honeydew is contact-, splash- or insect-dispersed.

The presence of honeydew at harvest can make swathing and combining more difficult. Late season scouting and field monitoring will help to develop harvesting/seed cleaning schedules and identify potential problem fields or areas that will need increased monitoring in the 2021 season.

The easiest way to scout for honeydew is to gently brush the flowers and developing seeds with your hand as you walk the field – if you feel a sticky substance, it may be honeydew from ergot. Aphids, if present, can also produce a sticky substance called honeydew, so, be careful not to confuse ergot honeydew with honeydew secreted by these insect pests.

Upon closer examination, ergot honeydew can often be seen being exuded directly from infected florets (red arrows).

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).