![]() They get separate infections while in the hill. Potato tubers are often infected in the field after the tops have been blighted. The sporangia serve to spread the disease in the growing season. 22.7 E) of the pathogen pushing out through the stomata. ![]() It consists of sporangiophores and sporangia (Fig. Under moist conditions they decay and emit a characteristic offensive odour.Įxamination of the lesions on the lower surface of the leaf on a dew morning reveals a delicate growth of the fungus parasite in the form of whitish powdery bloom. The blighted leaves curl and shrivel in dry weather. The disease generally first attacks the leaves, and petioles near the ground and the lesions appear on the lower surface of the leaflets on individual plants and then spreads upwards.įinally, a rapid and general blighting of foliage occurs. Under favourable conditions (low temperature and high humidity) the lesions rapidly increase in size involving the whole surface of the leaf. These appear on the tips and margins of the leaflets, rachis, petiole and stem. The disease makes its appearance as small, dead, brownish to purplish black areas or lesions. The conditioning factor is the favourable environment. It may appear as well at any time during the growth period of the plant. The disease first appears on the tops of the plants generally after the blossoming period but mostly in the month of January. In severe cases of infection there is complete loss of the crop, Infection also results in the decay of tubers in the field and storage. Consequently the tubers remain small and reduced in weight. Severe damage to the foliage shortens the growing season (Fig. ![]() The damage caused by the disease is frequently very high. ![]()
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