Hop (Humulus lupulus): Downy Mildew
Note the shoots with shortened internodes, characteristic of hop downy mildew
From OSU University’s Website: content edited by: C. M. Ocamb and D.H. Gent
Aerial spike present on hop bine
Cause: The fungus-like microorganism Pseudoperonospora humuli persists from year to year in infected hop crowns or plant debris in soil. It is an obligate parasite specific to hop. Disease is promoted by wet or foggy weather.
Symptoms: In early spring, spike-like infected bines rise among normal shoots from the crown. Spikes are silvery or pale green, rigid, stunted, and brittle. The undersides of leaves may be covered by profuse sporulation by the pathogen and appear dark purple to black. Tips of normal branches may become infected and transformed into spikes. Leaves of all ages are attacked, resulting in brown angular spots. Flower clusters become infected, shrivel, turn brown, dry up, and may fall. Cones also are affected, becoming brown. Severe infection in some susceptible cultivars may produce a rot of the perennial crowns.
Hop cone with downy mildew infection
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