Technologies developed to avoid frost damages caused by late frost during bloom in the fruit growing regions of Siófok and Debrecen

Frost defence is a serious challenge for the fruit grower. The problem is compound fi rst of all, as the grower needs a prediction to be prepared (Young 1920), Hagood (1967) or having an idea about the severity expected (Allen 1957). The frost threatens with more different damages in the horticulture than any other adversity in the USA (White & Hass 1975), as well as in other parts of the world. The prevention of frost (Rieger 1989, Kalma et al. 1992, Snyder & de MeloAbreu 2005) and mitigation of damages is possible by passive (indirect) or by active (direct) intervention. Passive prevention begins with the choice of the species and variety and the growing site, which means always to tackle the risks related to those decisions. The preparation of technical tools and fi nding the optimum of agrotechnical interventions including anti frost equipment or retarding blooming time, etc. (Lakatos et al. 2010). Heavy damages are often caused by the lack of any planned defence. Active interventions are actual any time when low temperatures threaten with freezing the tissues of the plants. Air mixing (wind machine) (Goodall et al. 1957, Crawford 1965) and irrigation are then actual (Davies et al. 1984, Cordy 1965, Brooks 1961, Gerber & Martsolf 1979, Synder 1986), as the most applied defence mechanism, but the induction of fog, paraffi n candle (Angus 1955) and the warming up by Frostbuster. The main use of microjets was originally the irrigation (supply of water) for agricultural and horticultural plants Technologies developed to avoid frost damages caused by late frost during bloom in the fruit growing regions of Siófok and Debrecen