Diseases

Downy Mildew of Hops

Humulus lupulus L.

A dangerous hop disease caused by the oomycete Pseudoperonospora humuli, characterized by systemic infection resulting in stunted shoots ("spikes") and necrosis of leaves and cones.

In the reference 60 varieties crop Common hop, where this is mentioned in the description.

The causative agent of the disease is the obligate biotrophic oomycete Pseudoperonospora humuli. The most characteristic sign of systemic infection, where the pathogen mycelium overwinters in buds and rhizomes, is the appearance of "spikes" — stunted shoots with shortened internodes and curled leaves.

On leaves, the infection manifests as angular chlorotic spots bounded by veins, with a gray or violet-black fungal growth forming on the underside under high humidity. Hop cones are also affected, leading to the formation of necrotic spots and a reduction in crop quality.

In hop breeding for resistance to this pathogen, standardized resistance genes are not used, and the trait of resistance itself is considered a complex indicator. The existence of clearly differentiated intraspecific races of Pseudoperonospora humuli is poorly supported in scientific practice.

General information about the subject — on the page Downy mildew.

Sources8

Varieties of Common hop mentioned in the description

Selection based on the description text, not on official evaluation: these data are absent from registers. For specific variety details, please refer to its profile.