The Hop Cyst Nematode, Heterodera humuli: History, Distribution, and Impact on Global Hop Production

Humulus lupulus (commonly known as hop) is an herbaceous plant that is used in brewing throughout the world. Hop cones are an essential ingredient in the production of beer, which makes hops of critical importance to global craft beverage industries. The hop cyst nematode, Heterodera humuli, is a plant-parasitic nematode with the potential to substantially limit yields of hop. H. humuli has been detected in many of the most significant regions for hop production worldwide, and infestations of H. humuli can consequently impact hop growth and limit cone production. Despite documented reports on the distribution of and damage caused by H. humuli since its description in 1934, there have been limited studies on the biology, pathogenicity, management, and consequences of infestations on hop production over time. Inconsistencies and gaps in the available information (e.g., the number of H. humuli generations per season, host status of alternate crops), exacerbate difficulties in understanding how H. humuli can be managed. Resolving the existing knowledge gaps identified within this review can lead to determining effective H. humuli management strategies for hop growers.