Bulletin number 6, 7/1 – 7/8/2020

Welcome to bulletin 6 for the 2020 growing season. Download the spore trapping potato data here and the sugar beet spore trapping data here. Both excel spread sheets require a password to open then. Email us to request access to the data.


No spores of late blight have been detected at any of the spore traps in Idaho to date. However, the Argimet weather station at Rupert recorded seven days (6/28 – 7/4) where there were more than 10 hours with the relative humidity above 80%. With the average max temperature on those days no higher than 60F that makes ideal conditions for late blight infection. As such, our Critical Humidity Periods (CHP) model is suggesting that the risk for late blight in this area is moderate. Across the rest of the state temperatures have gone up and humidity levels have gone down lowering the risk of late blight in these areas.

Spores or Alternaria solani were again detected at Aberdeen and Sclerotinia sclerotium (white mold) spores were detected at Aberdeen and Tetonia.

Sugar beet

Spores of Eysiphe betae (powdery mildew) were detected consistently at Parma (5 from 7 days) and 2 from 7 days at Glenns Ferry and Kimberly. It was detected once at Adrian. Visible powdery mildew was observed at very low levels at Parma Research and Extension Center. This now concludes our spore trapping alerts for sugar beet for the season as with visible disease present in several areas, a regular spray program should be implemented.