Spinach White Rust.White rust (Albugo candida) is a common but usually not serious disease. Local infection appears as pustules or "blisters" filled with sporangia on leaves, smaller stems, and floral parts. Pustules measure approximately 1-2mm in diameter and are white or creamy yellow. Systemic infections result in abnormal growth, distortion, and sterility of flowers or inflorescences. These abnormalities (or hypertrophy) are known as stagheads and consist mostly of thick-walled oospores.