Hops plant diseases are affecting hop plants in gardens. Verticillium wilt (VWC) is one of them. VWC is a fungal infection caused by the fungus Phytophthora cactorum, which attacks both young and old leaves of the affected plants. The disease causes the leaves to turn yellowish brown or even black, eventually killing the affected plant due to dehydration and wilting. The disease is not contagious and does not spread from one plant to another. Verticillium wilt is usually found in warm climates where temperatures reach 40°C or higher. However, it can occur at lower temperatures too.
Verticillium wilt affects both male and female flowers of the affected plants. It affects all varieties of hops including aroma varieties such as Goldings, Hallertau Mittelfruh, Saaz and Tettnang types. The disease can affect any type of hop, but it is most common in aroma varieties.
Symptoms of Verticillium Wilt:
The first symptom is the appearance of yellowish brown spots on the affected leaves. These spots may appear anywhere on the leaf surface, but they tend to form along veins and along edges. Leaves with these symptoms will die within a few days after being exposed to air. Dead leaves will turn brown and become dry.
The fungus can also spread to the petioles, stems and roots of the hops plant.
Second stage symptoms: during this stage, there are no leaf spots visible on the leaves. Instead, grotesque twisting and wilting of the vines is observed. The twisting will be more pronounced on the older leaves. These symptoms are not limited to vines.
New roots growing out from infected plants will also show signs of this twisting phenomenon.
Treatment for hops plant diseases: Once the vines start wilting, the fungus has already invaded the vines and roots of the plant. It is essential to destroy all infected vines as soon as possible. This can be done manually by digging around and removing all the infected vines. Using sharp pruning shears, cut off all wilted and dead vines.
Using a small knife or a shovel, dig around the roots of the infected plant. Make sure to remove all vines that have wilted. Next, apply a suitable fungicide based on the type of hop plant you are growing. Common hops plant fungicides are: Maneb, Ziram and Zineb.
It is essential to apply these fungicides before symptoms start showing up on the plants or immediately after you remove all infected vines from the plants.
Hops plant diseases can be fatal if left untreated. Make sure to treat all plants in the infected garden as soon as possible. If fungicides are used, make sure to apply them regularly so that no new infections appear. Good maintenance and sanitation will also help in preventing hop plant diseases.
Powdery Mildew on Hops
Powdery mildew is a fungal infection of the plant’s leaves and stems that appears as a white or grayish powder. It slowly destroys the plants by preventing them from absorbing nutrients from the soil.
Powdery mildew is caused by a fungus called Sphaerotheca humuli. Humidity and poor air circulation are the main factors in its appearance. Hops plant diseases are most common when temperatures are between 50-90F.
The disease first appears as small, white spots on the leaves of your hops plant. The spots will soon grow bigger and take on a powdery appearance. Leaves will begin to wither and fall off the plant, and this will quickly spread to the rest of the plant unless it is treated.
Sources & references used in this article:
Occurrence of Viroids in Commercial Hop (Humulus lupulus L.) Production Areas of Washington State by KC Eastwell, ME Nelson – Plant Health Progress, 2007 – Am Phytopath Society
Mechanical transmission of Apple mosaic virus in Australian hop (Humulus lupulus) gardens by SJ Pethybridge, CR Wilson, FS Hay… – Annals of Applied …, 2002 – Wiley Online Library
European handbook of plant diseases by IM Smith, J Dunez, DH Phillips, RA Lelliott, SA Archer – 2009 – books.google.com
Soil management in perennial crops: orchards and hop gardens by J Lipecki, S Berbeć – Soil and Tillage Research, 1997 – Elsevier
Overwintering of Sphaerotheca humuli, the cause of hop powdery mildew by AS Liyanage, DJ Royle – Annals of applied Biology, 1976 – Wiley Online Library
Hops: Botany, Cultivation, and Utilisation. by AH Burgess – Hops: Botany, Cultivation, and Utilisation., 1964 – cabdirect.org