Hop pathogens can be transmitted in rhizomes and plants propagated from infected stock. These pathogens include hop viruses and viroids such as: Hop Latent Virus, Hop Mosaic Virus, American Hop Latent Virus, Apple Mosaic Virus, Hop Stunt Viroid and Hop Latent Viroid; and fungal and oomycete diseases such as downy mildew and Verticillium wilt. Hop viruses can be spread by insects such as the damson-hop aphid, the potato-peach aphid and green-peach aphid, and also transmitted mechanically by pruning and mowing tools.

Viruses can cause yield loss, reductions and ratio shifts in α:β-acids, as well as stunting, chlorosis, and slower growth. Carlaviruses and Apple Mosaic Virus are known to be present in hop yards in the Upper Midwest.

To avoid pathogen problems from diseases transmitted through planting stock, plant disease-free rhizomes and plants, sanitize pruners and other tools regularly, and prevent movement of infected plants onto your property. Where possible, plant disease resistant cultivars.

Other Resources:

UW-Madison Plant Disease Diagnostic Clinic

Hop disease and pest fact sheets:

Hop Viruses: Identification and Management

Hop Downy Mildew

Hop Powdery Mildew

Hop Aphid