White rust

Taxonomic position and pathogen nature: Albugo candida belongs to the kingdom Chromista, specifically the class Oomycetes. Although historically classified as a fungus, it is an oomycete, a distinct group of fungus-like eukaryotic microorganisms that are obligate biotrophs, requiring living host tissue to complete their life cycle.

Diseases and susceptible crops: This pathogen is the causal agent of white rust (also known as white blister). It primarily attacks members of the Brassicaceae family, including economically important crops such as broccoli, cauliflower, cabbage, mustard, rapeseed (canola), and radish. Wild cruciferous weeds often act as hosts, maintaining the pathogen population in the field.

Biology and life cycle: The pathogen propagates through sporangia, which are dispersed primarily by wind and splashing water. Upon landing on a suitable host leaf, the sporangia germinate and penetrate the tissue. The disease cycle is completed by the formation of oospores, which are thick-walled, resilient survival structures that allow the pathogen to persist in soil and crop debris for several years.

Conditions for spread and damage: The development of white rust is heavily dependent on moisture. Cool to moderate temperatures (10–20 °C) combined with high humidity, fog, or dew create ideal conditions for infection. The damage is characterized by the appearance of raised white pustules on leaves, stems, and floral parts. Severe infections lead to leaf drop, distortion of flower heads, and significant yield losses in terms of quantity and quality.

Protection and control measures: Effective management of Albugo candida involves integrated pest management (IPM) practices:

• Implementing strict crop rotation, avoiding crucifers for at least 3 years in the same field.
• Ensuring proper sanitation by removing and destroying crop residues after harvest.
• Managing cruciferous weeds in and around the field to eliminate alternate hosts.
• Using certified, disease-free seed and selecting resistant or tolerant cultivars.
• Applying fungicides proactively during favorable weather conditions if disease pressure is high.