Bulletin number 1, 5/25 – 5/31/20

Welcome to the first spore trapping report for the 2020 growing season. As well as spore trapping data, this year we are also adding additional information collected from bucket traps for insects starting from next week. We will continue to send out the weekly email report on Wednesday evening or Thursday morning and the spreadsheet on the website will be updated as information comes in.


  • Spore traps have been operation for at least a week in the Treasure Valley and Magic Valley. Spore trapping in East Idaho has commenced this week meaning the first spore update for East Idaho will be next week.
  • No spores of Phytophthora infestans (late blight), Alternaria solani (early blight) or Sclerotinia sclerotium (white mold) were detected this week (May 25-31) in any of the Treasure Valley or Magic Valley traps.
  • Despite a wet start to the season, no critical humidity periods have been observed in the last week meaning a relatively low risk of late blight based on weather models.
  • We suggest no changes to your planned spray program based upon data collected from spore trap sites and AgriMet weather stations. For early season late blight control recommendations check out this article.

Sugar beet

Spores of Erysiphe betae (sugar beet powdery mildew) were detected at an extremely low level at the furthest west spore trap on Saturday, May 30. We do not recommend specific treatments for it at the moment but growers in the Treasure Valley, especially with crops near or at row closure, should be vigilant for the disease.