Some diseases of horticultural and field crops.
During surveys undertaken in the kharif and rabi seasons of 1981 the following diseases were recorded for the first time in West Bengal, India: sheath blotch of rice (caused by Pyrenochaeta oryzae), downy mildew-white rust complex of Indian mustard (Peronospora parasitica and Albugo candida), downy mildew of cabbage (P. parasitica), anthracnose of yam (Colletotrichum gloeosporioides f.sp. alata), white rust of Amaranthus tricolor (Albugo bliti), white rust of Ipomoea aquatica (Albugo ipomoea-aquaticae), and damping off (Pythium aphanidermatum), sclerotial root rot (Sclerotium [Corticium] rolfsii), bacterial leaf blight (Pseudomonas syringae) and Cercospora leaf spot (C. beticola) of sugarbeet. Club root of Indian mustard (Plasmodiophora brassicae), leaf blight (Phytophthora colocasiae) and corm rot (Corticium rolfsii) of Colocasia nymphaeifolia, leaf blight (Rhizoctonia solani) of Amaranthus tricolor, bacterial leaf blight (P. syringae) of sugarbeet, and powdery mildew (Oidium sp.) of Aegle marmelos were recorded for the first time in India. Rice root gall (Meloidogyne graminicola) and root nematode (Hirschmanniella oryzae) were found infecting Echinochloa colonum, a common weed of upland rice fields.