Vili KURNIK, Vesna GABERŠEK, Mario LEŠNIK
pp. 23-30

Two trials were carried out on apple plantation in order to determine the phytotoxicity level of several copper formulations (fungicides or foliar fertilizers) which were applied during the apple blooming and shortly after it. Tests were performed with formulations based on copper calcium oxychloride (trial standard), copper sulphate, and complexes or chelates of them with amino acids, peptides, EDTA, urea and gluconic acid. Different formulations were applied 8 or 10 times in a rate of 200 g pure copper ions (Cu++) per hectare to trees of seven cultivars (Golden Delicious, Gala, Fuji, Idared, Breaburn, Jonagold and Elstar). Evaluations of fruit set (i.e. number of fruits developed per number of flowers) and fruit disorders (malformations, surface russeting …) were done. The highest decrease in fruit set was observed when applying systemic Cu-gluconate and soluble Cu-sulphate to Fuji and Idared trees. The most severe fruit disorders occurred as a consequence of the application of systemic Cu-gluconate, Cu-protein complexes and soluble Cu-sulphate to Jonagold and Golden Delicious trees. The highest portion of damaged fruit (18-22%) was observed after the application of systemic acting Cu-gluconate and Cu-protein complexes. New systemic copper formulations are thought to have higher biological efficacy to control the fungal and bacterial diseases of apples than the traditional fungicide preparations. In the case of high efficacy of newly tested copper formulations, especially against bacteria, the observed level of phytotoxicity could be tolerated in terms of acceptable economic losses due to decreased quality of fruits. The phytotoxicity levels vary significantly in different apple cultivars, which shows the need for development of specific cultivar related instructions for use of new copper formulations.

Key word: copper formulations, apple, phytotoxicity, yield quality

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