Abstract

Stalk rot of maize, caused by Erwinia carotovora f. sp. zeae Sabet (re-designated as Pectobacterium chrysanthemi pathovar. zeae by KELMAN 1974) showed first premature withering and drying up of the uppermost leaves which was soon followed by the lower leaves. The rot either extended from the base upwards (basal rot) or from the top downwards (top rot). In the case of basal rot, the leaves become yellow and the infected tissue becomes brown, soft, and water soaked. Internally, the stalk turns into a soft mass of disintegrated tissue. At this stage the plants usually topple over. A foul odour, accompanied with the presence of dipterous larvae on and in decaying tissues, are the characteristic symptoms of this disease. With the advance of the disease the stalk finally dries up into a conglomeration of dry and shredded or disjointed fibrous tissue. The top rot begins with wilting and drying up ot the tips of middle leaves of the whorl. A decay that continues rapidly spreads downwards throughout the stalk and the affected plants soon droop. The host range studies were suggestive of the fact that the maize pathogen, apart from causing the disease on maize, could produce soft rot in potato, carrot, onion, sugarbeet, sweet potato, papaya, cabbage, and many other plants and could also infect Sorghum vulgare, Pennisetum typhoidium, tobacco, and tomato.