LIFE CYCLE, FORECAST AND CONTROL OF GNOMONIA LEPTOSTYLA (FR.) CES. ET DE NOT.

Life cycle of Gnomonia has been investigated since 1971 in our institution. The pathogen overwinters in the infected leaves, sometimes also in the epicarpium of the fruit. By the end of February asci are formed in the fruit bodies, and during March the ascospores develop. The earliest time of sporulation was end of March in 1980, the latest time early May in 1986. The duration is about one month. The incubation time takes 3 to 5 weeks. After the appearance of the first symptoms the development of the conidia and secondary infections occur almost continuously until late autumne.

During the primary infection period the optimal spraying time can be suitably defined with use of the "spora-combine" (Véghelyi, 1976). Regular examinations give expedient information on time and gravity of infection to be expected.

Trials had been conducted to clear varietal susceptibility. None of the cultivars investigated showed complete resistance.

The most efficient control of the disease is a combination of the forecast-based spring-sprays and of a desinfection of the foliage in autumne.

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