Some disease symptoms were seen on Mustard plants in a field in Ropar during one our visits.
Small, localized white patches were seen on both the surfaces of some leaves. On other leaves, presence of large powdery patches – especially towards the leaf tips, as if the smaller patches had coalesced to form large infected areas. On observing a sample from the infected area under foldscope it was confirmed to be conidia of Albugo in large numbers.
Albugo attacks Brassica and causes white rust of crucifers and the symptoms are reported as shiny, white, smooth irregular patches commonly called pustules or blisters on the leaves, stems and other aerial parts of the plant. These pustules are initially formed on the lower surface of the leaf but occasionally may be present on both the surfaces of the leaf. The conidia are round to concavo –convex in view.
Drawing samples from various infected leaves exhibited some solitary rectangular structures too. On close examination it was confirmed these were conidiophores (Fig-1)which bear conidia (Fig-2) and these are borne in chains at the tips below the epidermis and the epidermis is ruptured the conidia are blown in masses.