Phytotoxicity on apple flowers of copper formulations applied for the control of blossom blight
2011
Lesnik, M. | Kurnik, V. | Gabersek, V.
The phytotoxicity to apple flowers and young fruitlets is an important concern when applying copper fungicides for the control of blossom blight caused by Erwinia amylovora. To determine the effect of copper formulation on the phytotoxicity to apple flowers different copper formulations were applied four times during blooming of ‘Gloster’ apples in an experimental orchard at the rate of 300 g Cu++/ha. The phytotoxicity level of traditional formulations (sulphate, oxychloride, oxide, hydroxide) was compared with that of some modern formulations based on copper complexes (gluconate, EDTA chelate, peptidate and amino complexes). Fruit set (i.e., number of fruits developed per number of flowers) and fruit disorders (malformations, surface russeting) were evaluated. Our hypothesis that the phytotoxicity level of copper on apple flowers increases with the level of systemic activity of the copper compound was only partially supported by the results obtained. The copper formulations examined in this study can be ranked by their phytotoxicity levels on apple flowers (and indirectly on fruit) from the highest to the lowest as follows: Cu-sulphate, Cu-gluconate, Cu-oxo-sulphate, Cu-peptidate, Cu-EDTA chelate, Cu-amino complexes, Cu-hydroxide, Cu-oxide, Cu-oxychloride.
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