In the years 1999-2001, efficiency of plant protection products in control of early blight (Altemaria so/ani) was evaluated in two series of field experiment. There were examined four contact fungicides: propineb (Antracol 70 WP), chlorothalonil (Bravo 500 SC), mancozeb (Dithane M-45 80 WP) and zoxamide + mancozeb (Unikat 75 WG), and two with local penetrant mobility proparnocarb- hydrochloride + chlorothalonil (Tatoo C 750 SC) and metalaxyl-M + mancozeb (Ridomil Gold MZ 68 WP). In the series I propineb (Antracol 70 WP) showed the greatest efficacy in early blight control while in the series II mancozeb (Di thane M-45 80 WP) did.

The studies conducted in two different localities revealed variable time of occurrence and severity level of potato early blight (Alternaria spp.). Each year at Stare Olesno the early blight caused considerable destruction of potato plants (90.2%-95.4%) while at Bonin the disease severity differed in particular years and ranged from 50.0% to 97.5% of destructed plants at the end of the growing season. Field trials showed good efficacy of fungicides selected for controlling the early blight compared with an untreated control. Spraying with fungicides limited development of the disease and increased tuber yield in the range from 21.9% to 60.9% for Bonin and from 13.0% to 101.9% for Stare Olesno surveys. The mixture of zoxamide with mancozeb showed the greatest efficacy.

The NegFry model used for timing the chemical control of potato late blight was validated in field trials at Bonin in the years 2001-2002 (4 trials). In these trials the number of fungicide treatments recommended by NegFry was about 34.5% lower (on average) than the number of treatments in a routine spraying scheme. This reduction was mostly the results of a delay in the time of the initial fungicide application and longer spraying intervals recommended by Negfry.