Podosphaera macularis

Britannica Hop and Strawberry Mildew

Podosphaera macularis is a species of fungus belonging to the family Erysiphaceae. It is a pathogen known to cause powdery mildew on various plants, most notably on hops (Humulus lupulus), where it can significantly impact the agricultural production of this crop. The disease it causes is characterized by white, powdery spots on the leaves, stems, and sometimes the flowers of the plants. If left uncontrolled, it can lead to reduced yield and quality of the hops, which are crucial for the brewing industry.

Description

Podosphaera macularis produces white, powdery fungal growths on the surface of the host plant. These growths are made up of mycelia and conidia, which are asexual spores that the fungus uses to spread to new hosts. The fungus thrives in warm, dry climates, which are conditions that favor the development and spread of the powdery mildew.

Life Cycle

The life cycle of Podosphaera macularis includes both sexual and asexual phases. The asexual reproduction occurs through the production of conidia, which are spread by wind to new hosts. Sexual reproduction involves the formation of chasmothecia, which are protective structures within which the sexual spores, or ascospores, are formed. These ascospores can serve as the primary inoculum for the disease in the following growing season.

Management

Management of powdery mildew caused by Podosphaera macularis involves a combination of cultural, biological, and chemical strategies. Cultural practices include selecting resistant varieties of hops, ensuring adequate plant spacing to reduce humidity around the plants, and removing infected plant debris to reduce the source of inoculum. Biological control methods may involve the use of beneficial fungi or bacteria that antagonize Podosphaera macularis. Chemical control is often necessary in commercial hop production and involves the application of fungicides. However, the development of fungicide resistance is a concern, and integrated pest management (IPM) strategies are recommended to sustainably manage the disease.

Economic Impact

The economic impact of powdery mildew caused by Podosphaera macularis on the hop industry can be significant. Infected plants may have reduced vigor, yield, and quality of the hops, which are critical factors for the brewing industry. The cost of managing the disease, including the application of fungicides and the implementation of cultural practices, also contributes to the economic burden on growers.

See Also

• Powdery mildew
• Humulus lupulus
• Integrated pest management