What Is It?

What Is It? | Facts in Depth | For the Professional Diagnostician

Hop Diseases | Downy Mildew

Hops Downy Mildew

Identification

Leaves

  • Angular, chlorotic lesions visible on the upper side of the leaf.
  • Purple–grey or black growth may appear on the bottom of the leaf or spike.

Spikes and Crowns

  • Production of “spikes,” which emerge from the crown and are stunted and chlorotic with yellow green, downward curling leaves.
  • Infected cones may exhibit dark brown discoloration.
  • Infected crowns of hops may show reddish-brown to black flecks and streaks.

HopsDM6_50Quality HopsDM5_50Quality HopsDM3_50Quality

Favorable Environmental Conditions

  • Moist environments with moderate temperatures.
  • Relative humidity > 70%.
  • Leaf wetness for 4-8 hours at moderate temperatures.

Often Confused With

Scouting Notes

  • Scout plants for purple-gray or black mold growth on the undersides of leaves.
  • Look for the production of “spikes” from new infected shoots.
  • Regularly monitoring the weather conditions required for downy mildew infection may help to predict disease infection time.