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.
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).
2019 was a low ergot year in bluegrass in central Oregon. Can you speculate on how that will factor into ergot pressure this year? In your sentinel plots at COAREC did you infest with sclerotia or are you just air sampling for “naturally” occurring ascospores? I’m asking in reference to the high spore counts on the first day of trapping.
Good questions. Low ergot pressure last year should result in lower ascospore levels this year. 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.
The counts from sentinel plots are from an artificially-infested area at COAREC. It should be noted that the spore counts presented are intended to show daily trends in spore production and do not necessarily indicate inoculum pressure in your field(s).