Blueberry rust

Naohidemyces vaccinii is a pathogenic fungus belonging to the Basidiomycota phylum. It is widely recognized as the causal agent of blueberry rust, a fungal disease that significantly impacts various Ericaceae species, including highbush blueberry and lingonberry. The pathogen is widespread in regions with temperate climates where these berries are commercially grown.

The disease manifests as yellowish to reddish-brown spots on the upper leaf surface, which later develop into distinct rust-colored pustules on the underside. These pustules represent the site of sporulation. Severe infections lead to premature defoliation, which severely limits the photosynthetic capacity of the plant, especially during the fruit-ripening stage.

The biological cycle of this pathogen involves an alternation of hosts. The fungus often utilizes conifers as an alternate host, where the initial spring infection stages occur. Once established on the blueberry host, the fungus spreads via urediniospores, which can be wind-dispersed over long distances, facilitating rapid secondary spread throughout the growing season.

Environmental conditions play a critical role in the epidemiology of this rust. High humidity, consistent rainfall, and temperatures ranging from 15°C to 22°C create an ideal environment for spore germination and infection. Dense canopies and poor air circulation within the field further exacerbate the spread of the fungus.

The impact of the disease is significant, resulting in reduced yields, stunted berries, and diminished overall plant vigor. If left unmanaged, the cumulative stress on the plant can lead to increased susceptibility to winter damage and long-term decline.

• Sanitary pruning to improve air circulation.
• Removal and destruction of fallen leaves and infected plant debris.
• Application of systemic fungicides at the first sign of symptoms.
• Selection of resistant or less susceptible blueberry cultivars.