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Protection against radiation frost damage of sweet cherries in the bloom stage by use of rain covers

Vavra, R., Jonas, M., Kadlecova, V., Bilkova, A., Zdarska, I., Falta, V., Litschmann, T.
Acta horticulturae 2019 no.1235 pp. 503-506
Prunus avium, cherries, climatic factors, cultivars, flowering, frost injury, fruit cracking, genotype, hybrids, orchards, rain, risk assessment, spring, temperature, trees, Central European region, Czech Republic
Covering systems are used in sweet cherry orchards to avoid fruit cracking and rotting damage during rains. An additional advantage of using covers is the reduction of the risk of spring frost damage. The effect of rain covers on radiation frost damage was evaluated in covered and uncovered orchards during the bloom stage on 11 sweet cherry genotypes (‘Adélka’, ‘Aranka’, HL 13420, HL 15463 (Elza), HL 16165 (Felicita), ‘Helga’, ‘Horka’, ‘Justyna’, ‘Sandra’, ‘Skeena’, and ‘Sylvana’) in spring 2016 in Holovousy, Czech Republic. During the tree flowering period (full bloom stage; BBCH 65), the minimum temperatures subsided below 0°C for six sequential nights in the uncovered orchards (April, 24: -1.6°C; 25: -3.3°C; 26: -1.3°C; 27: -0.8°C; 28: -2.0°C; 29: -2.0°C), and for five sequential nights in the covered orchard (April, 25: -2.0°C; 26: -0.9°C; 27:-0.3°C; 28: -1.0°C; 29: -0.7°C). Frost damage appeared in both evaluated orchards (covered and uncovered). Less severe damage was recorded in the cultivars from the covered orchard than in those in the uncovered orchard. The highest differences in the degree of damage between the uncovered and covered cultivars were recorded in ‘Sandra’ (34% damage in uncovered orchard; 5% damage in covered orchard), ‘Skeena’ (33% damage in uncovered orchard; 11% damage in covered orchard), and ‘Adélka’ (31% damage in uncovered orchard; 19% damage in covered orchard). On the contrary, the lowest difference was recorded in the hybrid cultivar HL 13420 (8% damage in uncovered orchard; 5% damage in covered orchard). Other genotypes demonstrated around 10% differences in damage severity between covered and uncovered orchards. Covering cherry orchards has a positive effect by increasing the temperature by approximately 1-2°C, resulting in decreased frost damage occurring during the bloom stage under the prevalent climatic conditions of central Europe.