Association or Mixed Infection of Downy Mildew and White Rust Disease Complex

The association of downy mildew (DM) and white rust (WR) infection on oilseed Brassicas, vegetable Brassicas, wall flowers, and stocks has been observed. The association or mixed infections, or DM-WR disease complex, or simultaneous occurrence of A. candida and Hyaloperonospora parasitica on leaves, stems, inflorescence, and siliquae of crucifers in nature is very common. A. candida appears first on leaves, which probably predisposes the host to infection by H. parasitica. The intensity of mixed infections varies from 0.5% to 35%, depending on local weather conditions. Severity of mixed infections on leaves is not related to infections on inflorescence. It seems that greater susceptibility of new inflorescence and their availability over extended periods of time are associated with this phenomenon. The hypertrophied and malformed inflorescences of B. juncea infected with A. candida are usually covered heavily with the white powdery growth of conidia and conidiophores. Albugo candida alone, on artificial inoculation of flower buds, induces typical hypertrophy of the inflorescence.