Lesson 3 - Hop Biology and Cultivation SAQ

*Provide short answers to the following questions:

• a) Hops are described as perennial and dioecious. What does this mean?
• b) Is there ‘a preference’ to cultivate male or female hop plants? Why do you think this is the case?
• c) What would result if hops were grown below the 34th parallel south (latitude)? Is there anything you could do to prevent/support this?
• d) Name four pests or diseases, and how they affect the hop plant.

Response:

• a) Perennial means that they live for more than two years, and thus do not need to be replanted every year. Dioecious means that a plant is either male or female.
• b) When cultivating hops as an ingredient for brewing beer, only the female plants are cultivated. Female plants produce hop cones; male plants do not. Male plants can be cultivated for the purposes of breeding new hop varieties, but they are usually kept far away from the female plants in a standard hop garden. If the male pollen fertilises a female plant, then seeds will form in the hop cone. These seeds were thought to be detrimental to beer quality and have no value for brewing. In addition, if the seeds were to grow, the hop plant that produced may be a different variety to the rest of the plants in the yard. 
• c) Hops tend to only grow between the 34^th and 55^th parallel, so below the 34^th south parallel would be too far south, meaning it would have shorter day lengths than what is required, resulting in low yields. To compensate, it is possible to install artificial lighting, to extend the effective day length. Another option would be to try and breed new varieties which can grow in shorter day lengths.
• d) Any four of the following:
  • I. Red spider mite – silver speckling and webbing on leaves; discolouration of cones.
  • II. Damson-hop aphid – results in a sooty mould that grows on the aphid honeydew secretion. This spoils cone appearance and lowers yields.
  • III. Powdery mildew – white powdery spots on leaves and stems; it can result in cone losses.
  • IV. Downy mildew – causes stunted growth and blackened leaves.
  • V. Verticillium Wilt – causes yellow patches on leaves, which then turn black.
  • VI. Hop Mosaic Virus – causes stunting of the bines, with translucent banding on leaves. Affects cone yield and leads to a decline in alpha acid levels.
  • VII. Necrotic Ringspot Virus – causes necrosis in the plant and reduction of cone and alpha acids by 50%.
  • VIII. Hop Latent Virus / American Hop Latent virus – may reduce alpha acid content.