It is important to remember that the spore counts presented below are intended to show daily trends in spore production 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.

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 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).

Low spore counts (between 0 and 10 spores) have been observed on most days, with the exception of May 15 when 212 spores were captured.

Accumulated degree-days as of May 23 were 513 in Hermiston, OR (solid 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 2018, accumulated degree-days were 596 (dotted line).

The COAREC ergot spore trap site was set up on May 1 in one of our Kentucky bluegrass research plots. The trap is located in a second-year, 4 acre field with a history of ergot. Dr. Qunkang Cheng, Postdoctoral Research Associate, is also investigating alternative spore trapping methods for wider use in the Pacific Northwest.

Low spore counts (between 0 and 9 spores) have been observed on most days, with the exceptions of May 7 (263 spores) and May 10 (77 spores).

Low spore levels (1 to 60 spores/day) have been observed at the HAREC site since our last update.

Accumulated degree-days as of May 16 were 442 in Hermiston, OR (solid 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 2018, accumulated degree-days were 476 (dotted line).

Updated HAREC spore counts through May 5 are displayed below. Low levels of spores (< 50/day) have been captured on most days.

Accumulated degree-days as of May 9 were 351 in Hermiston, OR (solid 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 2018, accumulated degree-days were 379 (dotted line).

The HAREC ergot spore trap site was set up in one of our perennial ryegrass research plots on April 24th. Thanks to Ms. Victoria Skillman, Faculty Research Assistant in Dr. Frost’s Plant Pathology Lab at HAREC, for helping us with our spore trapping efforts!


A pulse of ergot spores were observed at the HAREC site on the first day of trapping, April 24th, as well as on April 25th. Updated HAREC spore counts through May 6th should be available by the end of this week.


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 2 were 259 in Hermiston, OR (solid 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 2018, accumulated degree-days were 278 (dotted line).

For more details on the model and how it was developed, please see our recent publication in the journal Plant Disease (https://doi.org/10.1094/PDIS-05-16-0609-RE).

Updated spore counts from our spore trap sites are now available below.

In general, spore production has tapered off at most sites, though a considerable number of spores are still being captured at KBG-1 (central Oregon) and KBG-4 (upper Columbia Basin).

Spore production should decrease as daily temperatures begin to regularly exceed 80°F.

Field scouting for honeydew at this time can help identify infected fields which may present difficulties during harvest and seed cleaning operations.

Prioritize monitoring efforts in fields that were infected last year, as well as fields in close proximity to previously infected fields.

Honeydew and sclerotia have been observed in non-treated, artificially-infested plots in Madras, OR.

Cultivars with late emerging flowers may still be exposed to airborne spores or honeydew.

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

Infections that occur later in the season can result in the presence of honeydew at harvest, which can make swathing and combining more difficult.

Fields with honeydew should be monitored for development of sclerotia (before and after swathing).

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 2019 season.