Abstract
Tomato early blight in central Poland was caused by Alternaria solani (A. porri f. sp., solani) and A. alernata (A. tenuis). A. alternata was isolated more often than A. solani. All isolates of A. solani in controlled conditions killed tomato seedlings, while pathogenic isolates of A. alternata caused only slight seedling blight. In greenhouse tests A. solani proved to be strongly pathogenic for leaves and stems of tomato but A. alternata was weakly pathogenic. The latter species attacked only injured fruits while, A. solanicould penetrate through undamaged peel of fruits. Both of these species caused the same type of symptoms; the differences consisted only in intensification of disease symptoms. During 1974 and 1975 field tomatoes were moderately attacked by early blight. Thebest development of this disease occurred by the turn of August and September. Determinate variety 'New Yorker' was distinguished by more severe infection of stem parts of tomato whereas the fruits of a stock variety 'Apollo' were more strongly attacked.
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